Pakistan army is a manpower based land force which relies primarily on numerical strength of troops as source of power projection. Since Pakistan is a poor country and it has very limited defense budget, therefore it cannot spend sufficiently for full filling all its capability gaps.
Pakistan, being a densely populated country with limited job opportunities, will always have huge figure of young people available for recruitment in Army. Henceforth, army is not short of lives, but instead it's short of economics. The concept of Martyrdom is generic in both Army and nation which further increases the acceptability of life losses. Therefore, when such conditions persist within any force, then that force automatically develop high casualitues tolerance level.
In contrast, take example of NATO nations. They have very capable armed forces as they have state of art assets available, have support of huge defense budgets further backed by robust R&D and security infrastructure. Their forces, despite being much smaller in size, are far more capable. At individual basis, their troops are better trained, better adaptive, better educated, better fed, better equipped, better informed and are better supported during combat. Result? Successful Execution of missions with none to minimum casualitues. Since those nations have less population and for their public Armed forces are not very attractive profession, and they have high budgets available, thus they tend to focus more on saving lives.
Perhaps that's the reason that casualty figure of 100 due to IED/ambushes in Iraq compelled the British to switch to Armored Fox Hound as standard vehicle from defender jeeps. But for Pakistan, even after losing over 1000 lives, we will continue to operate what we already have. We simply don't have sufficient options available.