Sometimes an E-mail is used on other company systems as a log-in, in whole or in part. I used to sympathize with past co-workers who had names much longer than mine, imagining them having to type "really_long_first.really_long_last@company.com" just to log into some web site.
I've also seen IT people enforce their random rules on everyone, leading to things like "rba186" as someone's actual E-mail address name instead of something meaningful.
So yes, choosing your own log-in and E-mail name would be pretty nice.
My school did your initials + 4 random digits, presumably to help prevent collisions and spam. It was pretty decent, actually, because you kind of got in the habit of chanting out a username in the same pattern, "a b c, 12, 34".
Works better than my current company, which does first initial + middle initial + 5 letters of your last name.
I've seen initials used too, which is at least a nice hint; but the case I based the example on conjured these characters essentially at random. The real kicker was that they were forced upon users in Unix environments who had been using CVS, Subversion, etc. and went from seeing useful log messages like "changed by jsmith" to aggravating ones like "changed by rjx133".
I've also seen IT people enforce their random rules on everyone, leading to things like "rba186" as someone's actual E-mail address name instead of something meaningful.
So yes, choosing your own log-in and E-mail name would be pretty nice.