Yes, obviously they’re for communicating with other drivers, what gave you the impression I meant otherwise? I was responding to this in your last post:

Unless you turn your blinker on to let people know your want over how is anyone going to give you enough space to merge in? […] You need to hit the blinker to let others know you want to move then check for space.

There are a lot of times where it makes sense to wait for a gap in traffic, rather than asking people to let you merge. And in those situations you would check for space before turning on your signal. You should still use your signal, even if you know you already have space to merge.