More and more

Yes, indeed. (1) is more 'active'-- it is more immediate for the listener/reader.

So '--er and --er' doesn't have to be somthing in progress?

Not so as to require the continuous aspect, Taka. It is expressing progress in a different manner-- a gradual accumulation of instances, perhaps:

Fewer and fewer people smoke these days.
Traffic has become heavier and heavier on my way to Totsuka recently.

Maybe this is trivial, but what exactly is the difference between a continuous aspect and a progressive aspect?

Absolutely nothing. At some point between the end of my university years (the late 1960s) and the onset of my English teaching career (the early 1990s), the word 'continuous' came into favour over the mysteriously obsolescent 'progressive'.

I understand.

Thank you, MM!

Oh, by the way, is the word 'progressive' going out of use, or becoming 'obsolecent' in general??

'Progressive' is still floating around as a synonym, Taka, especially among the more conservative prescriptivists. The far left descriptivists have gone on to call the aspect 'durative' -- a word I rather like, actually. I think I shall start using that.

Good night.

OK. So it is a bit obsolescent, but only as a grammatical term, right?

I believe it is still widely used in daily life.

Anyway, thank you again, and Oyasumi, MM!