meaning of "not as common"

Question

A teach in an English lesson gives this example

"I went to the store"

and then explains

whenever you have a movement, and you have a destination... So by movement I mean: "go", "walk", "drive", "take the bus", for example. Anything that involves you moving or going somewhere and then you're talking about the destination, - means the place that you are going to -, it's always going to be "to". And this is very much a preposition showing direction. Okay? Now, there are of course exceptions. There are situations where you can use "for". "Head for the hills", "Make for the lobby", okay? But very, very specific situations, very specific verbs and you're not going to use them that often because they're not as common.

where the phrase "not as common" is used.

I found lots of people also use "not as common", and some of those are "not as common as"

I googled "not as common" and got "it's seen around but not a lot", which is good explanation though, I still cannot get a clear understanding.

If I substitute the following for "not as common", do the sentences mean the same?

1. not very common
2. not so common
3. not too much common

Answer 1

It means that it's not as common as something else mentioned before.

The fact that (something) is very common is established first by saying for example : You can see it anywhere , it's widely available...etc then something else in same category is mentioned that's less commonly used/observed/encountered/known.

You can think of it this way :

(the thing I have just mentioned is) not as common (as the thing I previously mentioned )