As a guy that's played with and hunted with lots of different bullets over the years, I'll try to answer your question.
First of all, I like to experiment and see how these different things shoot and work on game. That's probably the biggest reason.
When I started hunting big game, back in 1956, if you used an '06, you were advised to use 150 gr. bullets for deer and like sized game and 180 gr. bullets for larger stuff. That's because the 180 gr. bullets of that time were designed to hold together, and penetrate. They didn't expand rapidly which helps when tring to kill deer. So one was advised to use the 150 gr. loads which did. If you needed something to hold together and penetrate heavy muscle and bone, you were advised to use 180 gr. or even 220 gr. bullets. that's because the 150 gr. bullets of the day didn't hold together well.
Today we have alot more and much better choices. The 180 gr. Nosler Partiton, for instance, open quite rapidly. The Berger Bullets, I'm told, are even more explosive. If you insist on 150 gr. bullets, then one can choose either the Barnes TSX if you need alot of penetration.
The other factor can be cost. Lots of us, including me, like the cheaper cup and core bullets for practice and the more expensive premium bullets for hunting.
There are those who insist that one basic bullet will do just fine and it need not be a premium. Not my experience. Often yes, they can. But not on marginal hits. Since I spend alot of money to go hunting, I find even bullets that cost a dollar a piece to not be a significant cost. E
