Why does the future always have to be liberal?

[Lumine]

It doesn't.

Or to be more precise, if the definition of "liberal" is of change to the status quo and "conservative" equals preservation of a given order, then obviously the future will be constantly more "liberal" under such simplistic terms. Using a more complex but more realistic view of liberalism, conservatism, socialism and other ideologies you'll find that history offers plenty of examples of changing societies and cultural views that become more conservative, even if you want to restrict that term to a specific type of religion-based social conservatism (which a nation can perfectly become more of).

If the question pertains specifically as to why American conservatism doesn't seem as viable an option in the future as American liberalism seems to be, I'd say you'd have to blame intense political ineptitude, dysfunctional organization and coherence, and of course, an excessive reliance on tired soundbites that are meant to represent conservatism. The most glaring example would be a GOP debate like the 2016 ones, which were a constant use of empty soundbites by almost every candidate on almost every debate and which, rather than an actual and inspiring vision, were reduced to saying "taxes", "Ronald Reagan" and "Obama" every five seconds.

And well, the current White House certainly doesn't help the case for American conservatism...