In parliamentary republics, why can't the parliamentary election and the presidential election happen on the same day?

You would think that it is more efficient for both the parliamentary election and presidential election to happen at the same time so voters don't become fatigued with politics.

I'm curious if there are any practical reasons for not synchronizing both elections in parliamentary republics?

Examples:

• Ireland
• Finland
• Iceland
• Lithuania
• Slovakia

Additionally, how does this arrangement affect voter turnout? Do they experience voter fatigue? Or inversely, does it actually improve democratic participation for some reason?