Just because websites can exist. Sometimes things are done for fun, or just for the sake of it.
This perspective declares all the personal websites of people worthless, however, they are priceless.
Because people's curiosity and creativity is priceless as well.
Similarly, why create art and share it around if it doesn't bring in customers? Why make music, take photos, dance? Do we live to serve customers, or do customers' existence serve us to live a better life?
Questions, questions...
If anything, it was a bit of a chore while keeping in mind that chores aren't necessarily a bad thing, e.g. tidying your kitchen after a meal is a chore, but it's satisfying to complete the chore as the alternative is not only a messy looking kitchen, but the hygiene issues which come with it. It's just something which needed to be done.
The once off nature, scope and priority were so minor that it wasn't worth the hassle of actually paying, but if free wasn't an option we would have either used my Claude sub or she would have just paid, no big deal.
Of course, those are all great reasons to make a website. But this website was for a woman's psychology practice. I don't imagine she made it for fun or to express her creativity. The purpose of a psychology practice's website is to tell people about your psychology practice, so they will either sign up ($) or find information they need more easily (higher satisfaction → $).
If OP's mother runs a donation-funded pro-bono psychology practice then you can translate the dollar signs to units of happiness or whatever (which I would imagine is her real goal regardless).
This person is spending her time to create the website (with ChatGPT's help). How much is that time worth? Of course when it's your business hourly pay is tricky, but I imagine she values her time highly enough that $20 is not worth very much of it.