It was ever thus, it would seem - and not just in acting. When I was a vanilla guerila, fighting my way through the corporate jungle, I'd often get asked to fill in this or that application form for a job or whatnot. Oftentimes, the form would make War and Peace look like a postage stamp and be structured like one of those make-your-own-adventure novels popular and welcome as an alternative to computer gaming in the 1980s. You could spend months working on completing the form, researching past misdemeanours, wiping the dust off diplomas you haven't seen since God was an embryo in the celestial milkman's eye and writing, in your best capitalised copperplate, all you've achieved and what you can do for the company. Then, task completed you trot down to the post office like a good little boy/girl, stick a copy of War and Peace on the envelope, post it and wait. And wait. And wait. If you're lucky, all that that work gets you is a curt obese Erithacus rubecula saying the position has been filled, signed pp the company. If you're very lucky you'll get a nice personal note saying thanks but no thanks, we'll keep your details on file (usually file 13). It can be crushing. And don't even get me started on computerised forms which, if badly designed by the lowest tender, go on and on and on forever.
The self-tape is, to my mind, the actor's version of the application form. Curricula Vitae are much better, with the actors' version being the showreel. The parallels aren't exact, but if the casting director can't see what you're capable of through a showreel, either your showreel isn't very good, or the casting director isn't up to snuff.