All I do is BIAB, and I always sparge. I found that if I don't, my efficiency is a bit low. Typically im at 74% by doing the mash with 2/3 to 3/4 of the total water for the brew, and then I sparge by pouring water over the grain bag once ive pulled it. I typically set a clean grate over the kettle and put the bag on top of that for it to continually drip back into the kettle, and ill pur my sparge water over that. Some have suggested dunking the grain bag into your sparge water and letting it sit there ~15 mins while you start your boil, then pulling the bag and pouring that water into the boil kettle. Both ways are super simple ways to get more efficiency out of your grain.
But I agree, totally not necessary. Grain is cheap and if you have the space for a bigger grain bill, just use more grain to get where you need to be.
Its really up to you. Whichever way you do it, just plan it out accordingly.