There’s a song whose lyrics include Must I always be waiting on you and I can’t always be waiting on you.
When I hear must I always be waiting on you, I can’t help picturing him wearing a bowtie and holding a tray of canapés and caviar. Waiting on should be reserved for what a server does for people in a bar, dining establishment, or cocktail party; he or she waits on them.
If you’re sitting around and doing nothing until a guest shows up for dinner, however, then you’re waiting for him or her.
Don’t use wait on (serving someone) for wait for (putting your plans on hold). We wait on tables, and we wait on customers, but we wait for colleagues to show up at the morning meeting, and we wait for the next train.
Sherry
Everything Language and Grammar 
I recall one more instance where we use “wait on”. In the context on computers, we often use “threads waiting on a semaphore”. I am not sure how correct is this usage grammatically, though.