Do philosophers always embrace rationalism? Why not irrationalism? What's so bad
Philosophers are generally speaking fans of reason and rationality, but there are exceptions, e.g. David Hume, who wrote that reason is a "slave to the passions." There is also, often, unclarity about what the reasonable or rational thing to do is.
In response to your final question: voting for a political candidate based on the attractiveness of his wife is inadvisable. If human flourishing in the future depends on who is elected, then voting in this way undermines your own interests, not to mention the interests of others.