This is a US based article and it may have a slightly different connotation south of the border.   In jobs where tips are earned, the employer can pay less than minimum wage.   Some 20 states pay a "tipping wage" of $2.13 per hour.   The goal is to ensure the employees wages make it to the state's minimum wage, with tips.   In the US your tip can be making up a significant portion of that server's  wage.

Hoteliers are trying hard to get patrons to tip  cleaners.  This will eventually allow them to reduce the Chamber cleaners wages to a 'tipping wage".  Nice, eh? 

I do see tips being requested almost everywhere.  I ignore them most of the time.   I do not tip when I buy take-out food.  I tip cabs, my barber and I tip a minimum of 15% and rarely more than 20% when I sit down to eat.