The second kind are entirely aware of this phenomenon, and take steps to avoid it. Ben Folds springs immediately to mind, he says in "One Down":
I'm really not complainingCounting Crows, in theory, are of that second grouping too, at least to some extent. Recovering The Satellites might have been mainly about Duritz's post-fame breakdown, and "Have You Seen Me Lately" might just as well have been entitled "Just Because You Buy My Music Doesn't Mean I Want To Make Eye Contact", but Duritz at least had the grace to apologise for his dabbling in Second Album Syndrome, and point out that the rock star life style does genuinely have attendant problems. Ones that have to be considered alongside the obvious advantages, yes, but problems nonetheless.
I realise it's just a job
I hate hearing bellyaching rock stars
Whine and sob
'Cos I could be busting tables
I could well be pumping gas
But I get paid much finer
Playing piano and kissing ass.
So, whilst a lot of famous singers are miserable, whinging douche-bags, I do have sympathy with the line that it's a job with its own set of drawbacks.
If it is just another job, then, how about people do it fucking properly?
I remember watching an interview with Gomez during the six months they were the next best thing, and one of their three lead singers (I can't remember, but I think it was the one who sounded like a leopard singing through a suede balaclava whilst being wanked to climax) was whining about how they don't like playing their songs the same way they recorded them. "That's boring; who wants to do that?" Well, maybe no-one. But if this is a job, then I couldn't give a flying fuck if you're bored, do your job. Sing the fucking song I paid to hear.
The Rolling Stones have the same problem, insisting on peppering their set-lists with their newer, far crappier songs. "We get more of a buzz playing the new stuff", they claimed at one point. I don't care. People paid seventy-odd quid for your gig, and it wasn't to listen to Mick Jagger play guitar. Sing "You Can't Always Get What You Want". Do your job. 
The 10% of Wednesday's Crows gig that pissed me off was an off-shoot of the same problem. The Crows have always had a habit of reworking their songs, adding sections, mixing them together. I tend to be OK with that in this case, mainly because they tend to work really well (and if I like songs X and Y Im generally going to be OK with the song (X-a)+(Y-b), where a is a verse and b is a chorus, or sometimes a middle eight). What doesn't work, and will carry the death penalty as soon as I finally work out how to rule the world (or at least the music industry) , is just randomly making up tempos and melodies for each line. Mr Duritz; you are not Alanis Morissette. Also: Alanis Morissette is shite. And, whilst Duritz is choosing his pitch according to an arcane and baffling stochastic process, the rest of the band are playing the song the same way they always do. I paid forty squids to attend a fucking karaoke competition. With only one contestant. Who was retarded.
This nonsense must cease. I came to a gig to hear songs I like. Or songs I don't like, but might change my mind on, or even songs I haven't heard before. Not to hear songs that are structurally similar to ones I like, but have then been re-scored by a tin-eared idiot. You're trying to persuade people to buy your records; how is that going to work if you make all your songs shittier?
Stop fucking around. Do your job.
 I once heard Richard Burton point out "I've been rich and miserable, and I've been poor and miserable. Rich is better." Anyone who ever finds themselves with a bank balance in seven figures should be forced to have that tattooed to the insides of their eyelids.
 A qualification here. If a band in its declining years insists on playing their pathetic imitations of past glories in order to shift more albums, then I'm fine with that (disappointed, but fine). Even superstars need to put bread on the table (or cocaine on the silky thighs of a hooker). But whilst most bands make losses on a tour and thus need to shift units, the Rolling Stones make a profit on their tour. They could just play their best songs each time, and never sell another album, and still continue to swell their already massive coffers. Once you get to that stage, if your fans (read "customers") are telling you to get your head out of your arse, then maybe you should live the fantasy that you're still talented exclusively in the recording studio, and spend your tours just actually being good.