They should, yeah. But sometimes they pick someone because everyone else picks that teacher/advisor/etc. Or they pick a
coach but that coach is a crappy letter writer. Or they pick the engineering teacher because they want to be an engineer and figure that letter would look good, but really the engineering teacher doesn't know the kid at all and has nothing he/she can say to make the kid stand out.
With good coaching, kids should be able to choose good letter writers. But it doesn't always happen.