Glad you brought this up Curtis:  a hidden subtext to most efforts to raise minimum wage rates is the fact that many union CBAs have negotiated wage rates that are tied to the minimum wage rate.   The union scale wage rates automatically adjust up in line with a formula set forth in the CBA whenever there is an increase in the minimum wage rate, and the union workers do not have to wait for the end of the CBA to renegotiate a wage increase in order to keep pace.
So, if you increase the minimum wage to $22 an hour over 4-5 years, you will be creating automatic pay increases in similar amounts on most union workers.  So, the economic impact on business is not limited to just those businesses who employ minimum wage workers.

Unions know this, and that's why they support politicians who push hikes in the minimum wage.