What does the service industry say about the other side of tipping?

There is a workman in our home at this moment.

he has cleaned our furnace and installed an air conditioner which we bought through his company last year. He knows our furnace is old and will need replacing sooner rather than later. he had every reason to assume we'll have him back. up to that time he had been prompt and courteous.

we recently did some reno work and had to have the furnace and AC cleaned. after he was finished cleaning he addressed some issues with drainage and we gave him a $20 tip on a $100 service call.

days later there was more dripping and we called him to come back

2 days in a row he was a NO-SHOW without even a phone call.

is this what we should expect when we tip?

we have a pool guy who changed his attitude after we tipped him as well

its as if we are now taken for granted as good customers so they DONT have to treat us well any more

can anyone offer a single reason to keep tipping people when this is the attitude of the generation

TO

INSURE

PROMPTNESS

T.I.P

Does it mean that any more or is it just another subsidy that you expect and for which you don't feel the need to give any value back