And if you bump everyone to $20, things will get more expensive and then you'll have to bump them to $22, and then everything will get more expensive so you'll...
The "historic raises in the minimum wage" were also very conservative and decried by proponents of $15/$20/whatever minimum wage as being too low. A one time pay bump won't cause serious issues, but giving in to ever increasing demands for minimum wage (ie. $15 last year, $20 this year, $25 the year after) will.
Minimum wage used to ride regularly, then since 2005 has remained constant while in real terms reducing by about 40%
[1] https://www.statista.com/statistics/1065466/real-nominal-val...
Except that if you adjusted the minimum wage in 2005 to account for inflation, you'll only get $7.93 today[1]. I doubt the people clamoring for a $20 minimum wage today are doing it on the basis of "keeping up with inflation".