Is there any relevance to Thor getting his hair cut other than comedic value? It was a funny scene and leads to a small joke in Avengers: Infinity War but since there is no 'Samson' like effect is there some symbolism or comic reference I'm missing?
Although the haircut scene doesn't affect the movie's plot and is played for laughs, it also works as part of the movie's symbolism.
Over the course of Ragnarok, Thor is stripped of almost all the accoutrements we associate with Thor. He loses his father, his hammer, many of his friends, half of his cape, his freedom, and then his hair.
(While his hair is perhaps not the most significant Thor-ish thing about him, it is noticed. As you mentioned, in Infinity War, Steve Rogers, upon seeing Thor arrive on earth with an enormous battle-axe, a sentient tree, a gun-toting racoon, and a robotic eye, seems to notice his haircut first.)
By the end of Ragnarok, he has also lost his eye, his sister, and his home. He learns that this doesn't matter — all that matters is him, and the people he serves and protects. Once he's learned that, he's finally ready to become King of Asgard, as he does at the end of the movie.
Miek's alive, the credits roll, and everyone lives happily ever, yes, yes they do, no, shut up, they go to earth, everything works out fine.
Apparently it was just because Chris didn't like wearing the wig anymore and it just took too long to get right as Eric Pearson has said in the below interview:
"When I arrived, there were certain things they had already decided," Pearson told CBR. "'We’re going to break the hammer.. Another one was, 'We’re going to cut the hair.' I said, 'Why?' 'Hemsworth doesn’t want to wear the wig. It takes a lot of time to get it right.'"