Is it okay to have a bath or shower every day?

It depends. Most people shower daily. If your hair can get greasy, shower daily. If it doesn't, take showers daily, but wash your hair every other day.

The idea of a daily shower was pushed by the soap companies with strong advertising about B.O. (Body Oder). The daytime radio programs aimed at housewives were called Soap Operas (now just 'Soaps') because of the heavy advertising by soap companies.

Before that, people showered or took a bath when they felt they needed it, but at least once a week.

If you lived in a cold drafty house with chancy hot water, you might understand their outlook.