Forget the binary between work/study visas and passports, it's a matter of specific context and international agreements.
The applicant's nationality and bilateral treaties can completely change the game, much more than the simple reason for the trip.
A Swiss citizen does not face the same administrative constraints for a job in Germany as an Egyptian, even if both are coming to work.
The hierarchy of requirements is not fixed; it depends on who is traveling and where more than just the "why" on paper.

In the Spanish context, choosing a two-week stay is not solely a budget constraint, even with more time available.
Here, it is often a social norm dictated by school holidays or summer closures of businesses.
Many families could afford three weeks but opt for two because it is the locally most practical duration to balance family life and work.
For example, colleagues take two weeks in August so their children can be with them before school starts, not because they lack money.