What is the purpose of ecchi/smut/borderline h /hentai?

Lists the definition of some of them > https://www.mangaupdates.com/genres.html

borderline H - refer to ecchi
Manwha - is the general Korean term for comics and print cartoons (common usage also includes animated cartoons). Outside of Korea, the term usually refers specifically to South Korean comics. South Korea is now one of the major producers of comics.

Basically some works will have erotic undertones but no sexual depictions (ecchi, non-h, mature/adult depending, etc) and others will contain sexual acts (hentai, mature/adult depending, doushinji, smut, etc)

You have to decide whether or not you feel up to reading/watching such material, but the question is a bit odd to ask (espically when your question includes hentai and you are on a hentai based site/forum). Makes me assume your a bit young for such things?

It's neither right nor wrong, everyone has the choice to read/watch and enjoy that stuff, or find it distasteful/offensive - it's their call in the end.

As for the purpose, I honestly have no idea. Some stories may move the plot thanks to erotic content, others use it simply for fanservice.

Story I guess, Normal hentai only last 1 chapter, some due stretch a few but they are rare. Your echhi/smut whatever, assuming it doesn't it canceled, lasts from 20-40 chapters, and some even go beyond up to 100 and such. There usually is character development, etc.

That's what I think anyways.

"Only a chosen few can appreciate the pleasure derived from what exists but is not seen."