My washing machine is enormous, so if I put in only my underwear, I'm just wasting water. I usually put in a few t-shirts, socks, or my pajamas in with the load. It saves time (because I don't have to do a second load), it saves water and electricity (good for the planet), and it helps clear out the hamper.
I would have to take the stance of placing all the washing together.
It is convenient , it is practical and you will save a lot of time.
There is no downside to doing this as everything is going to be wash and be
squeaky clean once it comes out.