Valid reasons to quit? i don't want to do it. But I see people leaving enterprises every 6 months.

A manager beating you up would be a valid reason...

Ir if you took a dump at meeting room

The reason why I quit from my last job was that I couldn't grow professionally (I was an intern and wanted to become a developer) and I needed more money.

Another reason I quit was that some things were simply going bad on the organization, specially for the systems department (they quit our "office" and moved most of the team to "office on wheels". I got moved to an office at the warehouse).

You don't need a valid reason to quit. Just quit

Advancing your salary the equivalent of one year or more, every sixth months.

If you constantly left jobs after 6 months you'd be considered a job hopper and that'd look rather bad on a CV.

People often change jobs every 2-3 years though and it's considered normal. Might be because of more money, more interesting work, annoyed with colleagues at the current place, fancy a different location, want experience in a different area, improve work life balance, cut down on a commute... the list goes on!

Not quiting that often will show companies you are more worthy to invest time in for actual training and getting to know the product. They will also be more open for your input.