In 1 line - PAK don't have the batting culture to post big scores by individuals. I must have upset lot of posters - need to explain it a bit.
First of all, many of the ODI 150+ are scored in last 5-6 years - a period, when PAK hardly had a top class ODI player. So, I 'll focus on the period from 1975 to 2010.
From 1975 to 1990, SCORING 150+ in an ODI was monumental task - if I take out Kapil, Turner & Amis's WC innings (played in 60 overs) against minnows (Amis's one was against IND in 1975), I think only player in that period had 150+ was Viv & Gower probably once. Viv is of his own class, therefore I exclude that period as well.
Now comes the business era - 1990s to 2010s. ODI rules changed a bit from 70s & 80s in favor of batsmen, but still it was relatively balanced & it wasn't easy to score 150+ in those period with some of the best ODI bowlers around & reverse swing was at it's prime.
In that era, I guess 90% of the 125+ scores were made by batsmen batting at 1, 2 or 3. Which is quite logical as well - 50 overs limited game, you give your best batsmen to bat most overs. BUT, you can't send sloggers to bat at 1, 2 or 3 against new ball - that can result once in a life time 102 (39) innings. The trick was quality shot making in 1st 15 overs, but having decent technique to survive the new ball - it's a selective aggression.
SO, most teams changed their strategy - they started to bring their best batsmen, batsmen who are aggressive by nature & hungry/capable enough to bat for long, long overs - in top 3, REGARDLESS of their Test batting position. All those players who has a 150+ in those days are basically Test middle order, but make-shift ODI opener. I am going from memory, a lot of middle orders were put in top 3 in ODI & they made it counted - MWaugh, Gilly, Panta (he was Test No. 6 till 2000, ODI No. 3 since 1996), Astle, Fleming, Sanath (He was a Test No. 6, was put to open & his success allowed SRL to continue as Test opener), Dilshan, Tend'kar, Ganguly, Sehwag (He was also Test No. 6 - opened in ODI & the fantastic 4, forced selectors to pick him as opener), KP, Amla, AB, Shiva, BC - all these are middle orders, either were sent to open or at least 1/2 spots higher than their Test number. The idea is simple - you are challenged to survive the first few overs, & then cash in for next 40 by dominating - that's the fundamental for a 150+ score.
Now, PAK's ODI batting philosophy is roaming around Geoffrey Boycott - that's Gillette Cup 1964 model. It's based on classical theory of "taking the shine off" on belters when 275 is probably at per. SO, players like MoYo & Inzi were pushed to No. 4 & 5 - so that they can salvage starts like 45/2 (14) or 73/3 (23) in larke lenge style. Only 1 world class player that opened (actually batted in top 3 - after Zed's retirement) had a 194, a 146 (?), couple of 135+ & a conversion rate of a ODI hundred in every 12 innings - that's mostly in 90s - 20 years later, it 's probably equivalent to 1 in every 6. Another attacking player that partnered Saeed had a highest of 137 (?) & for few times Inzi batted at 3, I believe he has couple of 125+ (in 45 overs match) against WI & a 140* in 1994 - you add straight 50 with that 20 years later.
It was by chance that Saeed & Sohail used to open for their domestic side, so that they could open for PAK. In fact, I think, even in domestics as well, these 2 probably were made to open for lack of spots - it's not easy to get a middle order slot for Karachi or Lahore for a youngster. Also, I am sure, they were lucky to debut in the era of Khan who had the vision of ODI batting. We give lots of credit to SRL for the pinch - hitting idea; but it was first Imran who actually tinkered the batting line-up promoting Salim Yousuf, Wasim, Qadir, Manzoor Elahi - even Sohail Fazal in higher order for a head start.
By any chance, just by any chance, if anyone dumb enough in PCB ranks could have ever thought of losing the match in 1st 10 overs (for intelligent PAK think tank - that's sending 1, 2 & 3 like Saeed Anwar, Md. Yousuf & Inzamam-ul Haq), we might have seen a bit different stats here today. Tom, Dick or Harry can hit 35 (23), may be sometimes 71 (52) or at best 135 (158), BUT you need class to finish like 158 (149) - even then you need to play almost entire 50 overs. That won't ever happen I doubt - that legacy of thought process abhi tak zari hai - now they are putting Umar at 7 & Maqsood at 6 & I am sure, if he continues like this, Rizwan 'll be made to bat at 7. On contrary, Azhar or Ahmed might play for next 10-15 years as opener & I 'll revert back to this post when they score their 1st 150 (even though the context has changed lot from 90s).
Long post - sorry for that, but I have to sum it up. Inzamam ul Haq was straggling big time in 1997-98 WSC - so that was the only time he was sent as opener. That's PAK thought process of ODI batting - top 3 spots in ODI are sacrifice - Kurbani ka bakra ko pahley bhezo, woo to out hona hi tha na.......
