It's par for the course, you can only have one official residence and you can't physically live in two places at once. It's not like a dual citizenship across two countries where you pay taxes to both, states require you to be a resident of just one.

You can live in another state and keep your registration, plates, license, etc. if it's a temporarily thing... students, military, etc. but outside of those situations, ANY state, note just PA, would require you to change everything over within some timeline.

When you "surrender" your previous DL, they just punch a hole in it and give it back to you. Although I do agree that it's a bit antiquated now that all 50 states are on board with the REAL ID driver's license thing, so it's now a federal database. But it made sense to require this back when 50 states all handled their licensing differently... if someone didn't meet the qualifications in one state but did in another, honoring another state's laws can undermine your own state's laws.. you see it with other things outside of drivers licensing, like whether or not states honor another state's concealed carry for guns or whatever. The entire point is to be able to enforce your own laws and regulations when someone new relocates on a permanent basis.

Sometimes you just have to change it if you want something, in your case MM. I had to change mine over while living in WA so that I could get in-state tuition while I was there in the military (although states have since changed their laws regarding instate tuition for military/vets). Regarding your vehicle registration, you may want to look into that... it's usually a two out of three sort of thing where you don't have to change everything over. I don't recall my specific scenario now but I was legally ok to keep my car plates in PA when I lived in WA despite changing my license and my state of record for insurance purposes.