Robbery is a violent crime (robbery, by definition, consists of using force or threat of force/intimidation) that places members of the public in danger. For example, last month there was a Nigerian bank robbery last month where bank robbers armed with assault rifles and got into a gun battle with police officers that left 16 people dead. [1]
Now, you could make the argument that running around with an assault rifle and firing at people is its own crime, but when you walk into a bank and hand the teller a note that says "Give me all the money in the vault," you are stating by implication that you intend to do [very very bad thing] to them if they don't -- you are using the implied threat of violence. (By the same token, if you confront people in an alleyway and say "Hey buddy, give me your wallet," you can't defend yourself in court saying, "But I never threatened people with violence!" The threat of violence is implied by your demand.)
So, in your question, you ask why bank robbery (a violent crime) is a jailable offense, while wage theft (a white collar crime) isn't. I think there's a lot of support for the idea that "non-violent offenders don't belong in prison (but violent offenders do)."
It's the same reason that burglarizing your neighbor's house while they're on vacation is considered by most jurisdictions to be a less serious crime than mugging someone: robbers don't just victimize people by taking their money; they also threaten the victim's physical safety. I personally would feel much more rattled if I had $200 in cash taken from me at gunpoint than if I had a client stiff me for $500.
[1] https://www.cnn.com/2018/04/06/africa/nigeria-bank-robbery/i...