Avast vpn and the launcher client/website

Is there anyway to use a vpn(im using avast) with the launcher, it seems to only work if i sign in through RL directly, otherwise it gives me this error even on the website:

Access denied

You do not have access to secure.runescape.com.

The site owner may have set restrictions that prevent you from accessing the site.

Why do ppl use vpn to play this game? It isn’t available in some countries?

vpn’s in general are used to protect your system and identity in a general sense online, not just to circumvent region locks. im just using it to be on the safe side mainly.