So What's the Deal?

Okay, so what's up with certain attacks not being able to be chained together? For instance, you can't follow up with an attack after the Trakeena assist, but you can with the extremely fast Drakkon assist. Or what about leader Kendall's Gun Bash block attack that doesn't allow you to follow up after it's hit but instead mutes all your attacks for 1 second?

Moreover, I'm just not understanding the logic behind not having the ability to simply combo normal blockable moves while other characters such as White Tommy, Trent, MMPR Kim, etc. have nearly unblockable single strike attacks to lead into combos.