They frequently already are. Even here in Canada[1] where any kind of "carry" is generally not allowed. Shockingly, thieves often don't care about gun laws though.
Your link refers to a single robbery which explicitly requires that you threaten another individual. "Thieves" encompasses far, far more than robbery, crimes where you needn't threaten someone else and carrying an illegal firearm becomes a liability.
Burglars in particular tend to target empty houses precisely to avoid confrontation. To bring a weapon only make sense if there is a chance of getting shot at.
Isn't "crime, done with the involvement of a firearm" also often more harshly punished than the plain crime itself? If a burglar is targeting empty houses, this would give them a strong incentive to not bring a firearm, just in case they get caught.
[1] https://www.cbc.ca/news/canada/toronto/toronto-police-cash-r...
As the saying goes, only break one law at a time!
This has to be made up.