Nowadays web email services like Gmail set the minimum standard for how email should work. You should be able to choose your email address from what's available, and also create new email addresses whenever you need them (with self service).
If the corporate email system cannot provide service that is as good, then people will start using services like Gmail instead. I see it happen all the time.
Personally I also regard it a sign of cluefulness to have an email address with very short local part. I always hated Gmail's 6-char minimum limit for usernames.
Recently I volunteered for a political campaign, and I signed in with a pen and wrote my email address on the sign-in page. It's mylastname@gmail.com. The campaign director saw this and said to me, "how were you able to get that address?" I said, "I've had Gmail since the day it was offered to the public in 2004." He said, "wow." Not a big deal to me, but email namespaces matter. I totally agree with the OP.
I have one for my wife, son, and I. It makes life so easy when people ask for an email address and I say firstname@firstnamelastname.com (and my surname is really short and really common). Invariably, some think you are some sort of uber hacker because you pay $7/year for this service.
And then they try to send mail to firstnamelastname@gmail.com :) I have a similar domain and people have a shockingly hard time getting it right: "Yes, "john" AT "j" followed by my last name, dot com"
If the corporate email system cannot provide service that is as good, then people will start using services like Gmail instead. I see it happen all the time.
Personally I also regard it a sign of cluefulness to have an email address with very short local part. I always hated Gmail's 6-char minimum limit for usernames.