The real promblem is that GENERAL midi is just THAT - GENERAL. It will never be all things to all people. It's a starting block, a template if you will. If something specific is bugging you .... you need to make it specific to YOUR needs. Thereis no way a programmer can anticipate the end result of each of the songs they create, because they will all be played on different media, in different ways.
Just use what works, and FIX what doesn't.
It's no ones responsibility to make EVERYthing work for EVERYone. That's YOUR job ... to personalize and perfect your art. Expression is a key element to excitement, and adding the sampled vibrato adds a realism to notes played in real time, that would be more difficult to do if you needed to access anothetr controller to get the effect. It's all ying and yang ......
you gotta give a little,
take a little .....
That's the story of,
that's the glory of ...
(well, you get the idea )