There are also another two aspects:

1) Bugs. Due alpha/beta there are loads of bugs which some players used to advance their chars. In release version this bugs would be fixed and people who used it in the past got certain advantages in compare to new, 'legit' players.
2) It's hard to 'return' to sandbox game. I felt it when I returned PG after two months break (check my past stream...). You don't remember anything, you got loads of unfinished in the past stuff which you don't remember where to do. So if there is a wipe - it's much easier to start from scratch, than going on with 'old' problems