With the ease of creating, or even purchasing, suppressors and the rarity of their use in crime I'd say the risk isn't high enough to deny use to literally every person that wants to use it for legitimate uses. It wasn't even an actual issue within organized crime when they passed the laws. They simply wanted to regulate them to only the rich like every other item they included in the NFA (they even wanted pistols but decided not to include it, likely because it wouldn't have passed). In the 30s only the extremely wealthy, including gangsters that the law was supposedly to keep them away from, could afford the $200 tax stamp.

Honestly, at a time rife with crime and corruption when the supreme court hadn't ruled the right to own a firearm to be protected by the second amendment, why would they say you need to pay an exorbitant amount to get permission instead of an outright ban?