I have been reading over and over how people take a rifle, lets say for example a 30-06, then they will load up 180gr bullets for elk and 150gr bullets for deer. Im curriouse of why some people choose to do that. I live hear in Idaho, I hunt elk and deer every year, and i use the same bullet for everything and it works great. So my question is Why do some people choose to have a load for deer and a load for elk?
.............Tend to agree with you...BUT! Variety as they say,,,,,"is the spice of life."
Many like or choose to experiment with different bullets for many reasons. Either to see what shoots better, for better BCs, marketing influences, influences from their own circle of friends, for different affects on game. All sorts of reasons.
The same analogy can be said for caliber and cartridge choices. For deer and elk, some use 25s, 6.5s, 270s, 7mms, 30s, 8mms, 338s and so on, along with a variety of bullet choices and weights for each caliber.
Your point is well taken, but bullet variety and caliber variety as well, is what makes hunting and shooting far more intriguing.
Not out of place to use a 190 or heavier 30 cal bullet for elk and the 30 cal 130s to 150s on deer.
The answer to your question is simple..........Choice!