I tend to accept positive comments with a grain of salt. I do think that people sooner compliment than criticize or insult, which leads me to place a lower value on compliments than some or maybe most people.
Some compliments are just so easy to give- some seem just plain empty by nature. "You're nice," yes, thanks, I haven't murdered anyone. I usually don't understand what precisely the person means, so it registers as useless white noise. I usually don't see compliments as telling of anything unless they can be explained or are relevant somehow. You say it is easy to not say anything at all, I'd say it's also very easy to be 'nice' for people who want to be.
I think most people say things with the main goal to make someone else better, which
by itself wouldn't mean they would lie. That does mean that some of them are, however, prone to exaggerating the importance of what they are complimenting. Sure, they'd say they won't lie, but in a dire situation they sometimes toss out multiple compliments ("Look at the bright side!") that creates a very pleasing image for the person they are complimenting (and sometimes for others, and most often- for themselves). If a person is an asshole but he is tidy, that complimenter will hyperfocus on how tidy they are and how positively it speaks of them as a person, but actually ignore the whole- turning a blind eye to the 'non-complimentable' parts.
Oddly enough, I do let pass 'polite'-style compliments. We're at a dinner and your extended military grandparents are here eyeing all of us. Sure, toss a couple compliments out unbidden. I know it's just something that the situation expects you to do.
I suppose with this I can say that I take compliments with a grain of salt- always, and-