I think that music show wins are important because it shows the artist/idols that what they have been working hard on has been appreciated by their fans or just the public in general. I´m not sure if I made sense XD

in the beginning, when a group is starting out, wins are quite important. But if a group is like Big Bang level, then I don't think a music show win is as important, although it's a nice gesture from the fandom.

It does, in my opinion. It either proves that you have a dedicated and big fandom or your song is well received by the general public that they vote for you, buy the song or listen to it enough. If there are groups out there who are not rookies anymore and haven't at least one win, they are considered very small and unknown. Which is true in every case I know of.

for the groups, probably, especially when they're newly debuted or still struggling to make a name I guess
for the fandom, something to cheer on (and something to fight for lol)
for a mere listener like me who just want to enjoy the song and want to stay low and quiet from fandoms, it doesn't really matter.

I think it's a kudos to a band that their music is well-received. And I think it matters a lot to companies, it proves that the group is good enough to keep going, I guess. But I guess it's nice to be recognized so I'm sure all groups are happy to win. If a group has won a lot of times, I think it might mean less than if it's the first win.