I think a lot of people complain more than compliment when it comes to service, because there's a (completely reasonable) expectation that the product/service/etc will be good, correct, valuable, etc. When that standard isn't met, people complain. When their expectations are met, that's status quo, and so they don't necessarily express gratitude.

Same with people and friends often enough - people expect others to behave well, treat them respectfully, etc. When people are mean, take what isn't theirs, lie, gossip, etc, people get upset, their expectations aren't met, and they complain. So again - when their expectations are met, that's status quo, and so they don't necessarily express gratitude.

I try to even the odds with those around me, at work, in my personal life, with service providers, etc. Sometimes I succeed, sometimes I don't, but I try