Bitcoin is volatile, fiat currency - especially if it belongs to an economically strong country, is much less likely to have large and quick drops. Not every use case allows hodling for years without touching your money.
Also Bitcoin is still considered an experiment, and there's no good way to predict its future. Just because it was going up doesn't mean it will be going up forever. Putting all your money into Bitcoin is unwise. So having some money in traditional banks is going to be a good decision for a long-long time.
Having money in bank and using a payment card is way more practical than spending lots of time and effort for trying to pay with Bitcoin in real life.