If you want financially sound reasons there are plenty, just the most obvious ones off the top of my head:
Opening the game to people with entry level computers (right now your only choice is to downgrade graphics to the point where EU looks like minecraft). Uh-oh 50 players on the same area? bye bye fps
Another reason? the publicity stunt. Laugh all you want, still effective. And this was the real reason behind VU10 wether you like it or not.
Another one? How about fixing a million bugs that are inherent to CE2 and the way it has been customized/implemented by MA in the past? I worked a lot on cryengine back when Crysis was first launched. Mostly LUA scripting for several mods back when crymod.com had thousands of visitors at any given time. I know for a fact that the current engine is pretty much the worst possible choice for an open world MMO, which means that whoever imposed it for VU10 didn't do the homework.
How about VR? lots of AAA game studios are pushing for it. VR cannot be done properly (or even half-assedly) with CE2. Terrible performance and huge dps drops on network events mean you'll have a lot of people puking their guts out soon enough.
There's more if MA really wanted to do it. The problem is they don't want to because they are lazy and have the minimum staff. It's always the same problem, always the same. This is, in part, why they break so many things on every big release.
In my opinion CE2 is a mess, it was intended for a very specific type of game (your typical story driven fps) and it does it wonderfully but little more.
But I agree 100% that we go in circles with this discussion, for years.
It probably will never happen, which is a shame.
Take care, it's not a bad question but it's one that has been asked a lot (even by myself several times)... sorry.
Just my opinion, it's ok to disagree