Just my 2 cents:
I do not agree that the game should be wiped between betas, it really makes no sense. But it should obviously be wiped before release. Of-course it depends what the devs want from beta, and if they want to mostly test the starting area and classes, but that again makes not much sense. I believe beta should be used to test all aspects of the game, but the biggest advantage devs can get from a wider audience, beta provides, is stress testing the system and test “border cases”, as a bigger audience is more likley to randomly produce some weird state that might brake the game. And if that is the actual purpose of the beta, than it really makes no sense to reset, because less people will want to rerun the initial part of the game so many times, the ‘higher level’ aspects of the game will be tested very little so the overall advantage devs could get from the beta is simply reduced. And who cares if balance was broken at early betas, or something silly like that. Its beta anyway, it will get wiped before the release. So I really see no valid reason whatsoever to wipe each CBT.
EDIT: the only valid reason I see for the data to be wiped, is that the devs are actually “lazy” to do data migration, since they are still developing the game and the data model might change between betas. It is way easier to just wipe every time than actually migrate old data to new data. But I think that is also bad, because they could use this betas to “practice” game updates, see if they can make major updates, with data migration before production. But maybe we are still so far from release, that all this does not yet matter, and we will see a couple of more CBTs and a long running OBT. In that case all this wipes kind of make sense, but this makes me slightly annoyed as I do not want to wait for another year for this game 