Because web browsers default "home screen" has a large text box by default. People think that's where the address goes, but not really, that's actually a web page which does search. Shame on us for designing it that way.

But on another note, it will be the day when your mother (or anyone else for that matter) types in 'www.walmart.com' and actually goes to 'www.target.com' (names taken from other examples that I've seen on Twitter).

That is already happening

I made a new webpage for my father, and my mother cannot open it, since google does not know about that and there are no links to it.

Maybe Firefox should change the default screen from containing search to containing the address bar instead. That way if you type in a proper URL there it should go directly to it rather than doing a search.

Not going to happen, that very search box is Firefox's main source of income.

There is unfortunately a tax on stupidity, and in this day and age it is paid with one's personal data to multinationals.