Although I am familiar with showcases at competitions, yes, I did miss your point. My answer is still the same, though.
Showcases can be performed in lots of places, including at ones local studio, to accomplish the purpose of creating focus and goals. Why pay the premium price to enter a competition, pay travel, spectator tickets, entry fees and pay for a showdance to accomplish the same thing? If you're going to be at a comp anyway, sure; why not? Otherwise, it seems to me an awful lot of hassle and excess expense.
Of course, if you attend an independent studio (many of which do not offer showcases) it sounds like a great idea.