The workshop has, to me, always primarily been a place to post work in progress mixes and get feedback on how to improve those mixes. Maybe the balance is off, maybe the soundscape is too sparse, whatever. If there was an issue with a track, the workshop was a prime place to find out what that issue was.
If there's a simple 1-10 system applied to all songs, then the workshop loses that purpose.
"Oh I got all 1s. I know it was bad and a very very rough WIP, but I'd like to know what could've been done to improve it."
"Not bad. A mix of 7s and 6s with an 8 or two thrown in. I wonder what they liked the most."
"Ah sweet, 9s and 10s. I sure hope that's not just because and there's actually a reason for it."
Those are three completely hypothetical thoughts that could be, well, thought if we relied on the 1-10 rating system and nobody ever explained their ratings.
One of the great things about the compos we've had in recent years is that even if there's separate places to vote and to post about the mixes, there's been a lot of good reviews posted about the songs in each round. And those often point out little issues that could be done to improve each track. Which causes the songs to wind up in the workshop when people want to improve them. And if they went from "Cool I know exactly what to do" and then they did it, posting it in the workshop for reviews on the improvements... a 1-10 system would be the complete opposite of that. No feedback, just a number. A number that can mean many different things to different people, depending on how they interpret the score, but generally a lower number is worse. Unless you're playing golf, which we aren't.
I think the Like system would be much more beneficial, as it prevents any negative reactions from a low score in addition to also showing how good it is. It might be even better if the Likes were hidden (as timaeus suggested above), as those would prevent people from liking on principle because the song has a lot of likes and instead would require them to listen to the song and decide for themselves.
And really, what use is the workshop if people are just liking without listening?