“in part because they’re afraid hackers could exploit those same back doors”
Not could, would. There is a 100% probability that if backdoors were built into encryption standards, they would be found and exploited. No matter how long it would take to find them, the reward is so great that it would justify any expense and effort to ferret them out.
It would not be limited to hackers either. Every foreign government on the planet that can afford an intelligence apparatus would be trying to find those backdoors as well, so this would compromise our domestic security in a very fundamental way that would outweigh any potential benefits.
The suitcases full of cash method works wonders for finding those “secret” back doors, especially if you’re a governmental actor.
I give it a month, tops. The government's security against "inside man" leaks is pitiful, and for every Snowden who makes great personal sacrifices to reveal the government's dirty deeds for principled reasons there are dozens of others who would gladly sell a backdoor key for personal profit.