For example, let's say you're the dealer holding this:





The upcard that was turned down was the

Everybody passes second round. So what do you do here? Would you call clubs? That's your strongest suit but it's also a next call. You might have one trick here from the ace. If that's trump though then the bowers can beat it. Odds are your partner doesn't have them or he'd have ordered you up.
You're also four-suited here and have no opportunity to create a void, so you can't count on trumping in when an opponent leads to your void. You have no real strength in any suit except clubs. If you make that trump then you might even weaken your strength in this suit because the Ace isn't boss in trump.
Would you try a reverse next call here, name hearts trump and hope that your partner is loaded up on red cards?