A like is not meaningless although it’s free. Likes can be used to show acknowledgment of having read the note, as a nod / agreement, and as a show of support for what was said.

We don’t always need to respond to everything. Real life conversations have ahums and “yeah” and “totally” or actual head nods and online likes sometimes take place of that.

Besides, it feels inappropriate to throw money at a note in some scenarios where a slightly supportive signal would be more meaningful.