It is not cock eyed if you have the whole picture.
If someone is employed and earns one salary (less than 22k) their tax affairs will be sorted out by their employer and they have no need to make a tax return.
Anyone who is resident in Spain and has multiple income streams, or earns their income tax free at source, receives pension income etc gross regardless of total income - then they need to make a tax return and be fiscally resident.
This has benefits and is of course the law, certainly for EU citizens.
I think there are other issues for non-EUers.