I have statistics. 2640 user accounts from 6320 orders.
Some customers are repeat customers, but even if we are generous and assume that the majority are not repeat orders (I'd estimate 25% are repeat orders), that's over 1/3rd that created an account even though I offer guest checkout without an account and don't really push them to create an account.
Interesting, thanks. But it is still complex: it surely also depends on what you sell and the average customer you have, and also if the users expect to have some advantages by registering.
For example, I personally like to be able to follow the order etc. but often online stores insist that I have to register for anything like this. If the order number and my name were enough, which technically should be, I wouldn't. But having no alternative, I do. So I count myself in "I would prefer not" but you see me registered and count "one of 3 who like registering."
I believe if statistics would be produced: the users mostly don't want them. The owners of the site and the programmers mostly do.