Why is the Hungarian Forint a weak currency?

I mean, Hungary is one of those countries that haven't made the switch to Euro (for perspective: both Bulgaria and Croatia adopted it) despite them being a member state. I know that HUF isn't strong (1€ = Ft 388, as of writing) but by having Euros: does your PPP increase a lot when visiting Hungary as a tourist?

I've heard that HUF is volatile as it inflates like crazy since it's weak against the Euro. Also, for Hungarians: does it mean visiting neighboring countries is expensive since most use Euro when you take purchasing power into account? The exchange rate isn't favorable for them as they would need to pay more.