@Hella Depends very much on the system. Pathfinder is very crunchy, so I don't generally run it. Crunchy systems can make chargen a PITA, yes.
The difference is that my DM is there, helping me, and is my buddy, and will probably get me into a character by the end of a conversation/session 0.
On a MUSH, I could wait days or weeks to get that character approved, especially if I'm struggling through the system. So, on a tabletop, if I have to roll a new character, I have lost an hour, and my four friends will go out of their way to help me establish my new character in the story.
On a MUSH, I'm now looking at being bored out of my skull with no way to participate for what could amount to half a month. Maybe one or two friends will actually interact with the new character as quickly as they interacted with the old and create a background that lets you jump right back in as an old friend or whatever. You're going to have to go through the same tedious small talk getting-to-know-you RP that you already did with the other 38 people to get re-invited into stories. So you lose a much bigger investment of time and energy. Which is why I don't think it's necessarily fair to get frustrated with MU*ers for not wanting to lose characters.