Since you seem to be having trouble with this concept... watch the video that YOU linked, and count the number of Enhanced Moves Liu Kang does. Or Johnny Cage. Very, very few? Yeah. What were you saying, again? =P
In Street Fighter, people use EX all the goddamn time. In MK, with some characters it's worth it, with some characters it's just not. And an option that is never useful is not an option, it's just clutter.
Been watching a lot of matches, and playing as well, and a well-placed Enhanced move can make all the difference. Of course, you have to make a call whether you're better off using a breaker or an Ex move. Just because you don't see them flying as much as in Street Fighter hardly means it's clutter. I agree that some Ex moves are more useful than others, but most of them have a good use. There's a reason every combo or strategy video says "And then use teleport because it builds meter".
Also, wanna base an uninformed biased opinion on an entire game by watching one video clip?
Street Fighter 2 sure did define the genre! Such an amazing fireball game! (the clip is a Japanese tournament match, btw)