I believe that the the M77s aren't as popular due to the angled front action screw and lack of aftermarket support compared to the likes of Remingtons and Savages. There was also the issue with the outsourced barrels and poor groups that Ruger suffers from to this day. Gun people do not easily forget such things usually.
but some of those old models had very poor quality bbls from new.
I have one of those - a 7x57 that I bought in 1977 - the thing shot patterns, not groups. Finally ended up with a properly throated Douglas barrel and Canjar trigger, which turned it into a real shooter. From what I've heard, the 7mm barrels were the worst ones - something about not being stress-relieved properly. My buddy bought one in 30-06 at the same time, and his has always shot supremely well.
What many people forget is, when the 77 first came out, it was the only real "classic" style rifle readily available - we were still in an era when the mfr's were trying to make their rifles look like a Weatherby, so, unless you wanted to pay major $$ for a custom rifle made in the classic Jack O'Connor style, you got high gloss Monte Carlo stocks and high polish metalwork (nothing wrong with that, to each his own). Plus, they were available in a pile of calibers (250, 257, 7x57, 284, 280, 6.5 RMag, probably others that I forgot) that weren't routinely available from R-P and W-W, so, we grabbed 'em!!
To the original post, I currently have 2, the 7x57 and a 280, and really like them. Sorry, no first-hand experience with either the MKII or Hawkeye.