Tthere is another possibility to express to have
to / to must => haber de. When we think about it
it's not so unusual since haber
had been a full verb for to
have to. Another question is what is said about
a culture that has so many different forms of to have
to (meaning more or less having no other choice than
to do something, even if you do not want to). However, this
is a philosophical question not necessarily a
grammatical.
Example
He de hacerlo,
si me guste o no.
= I have to do it whether I like it or not.