My reason why is fairly simple.
To succeed in politics, you must have a strong strategy laid out. Republicans have no such strategy. They are an outer party doomed to continually disappoint their most ardent supporters. This inevitable disappointment maintains a long-term cycle of failure. Still being relatively young, and hoping to maintain a very long-term outlook, merely scoring a temporary political victory that lasts for a few short years has no appeal to me whatsoever.
While it may be true that the Republican Party is capable of slowing the advance of the militant left by a few short years, that is all that it’s capable of before spending all of its capabilities.
The main reason not to vote, for any reason, is to preserve resources for a counter-attack.
To prepare for a counter-attack, you must bait your stupid enemy into sending all of his most valuable forces into an indefensible position, such as a valley or a plain. If the enemy is especially stupid and short-sighted, he will maneuver into such a trap in a predictable fashion.
Such a counter-attack would look something like a successful secession campaign in a major American region outside the core economic zone on the ‘Acela corridor’ between Washington D.C. and New York City.
The left was once managed by canny political operators. This is no longer the case. It is now primarily driven by idiots. Idiots are wonderful, at least when they’re on the opposing side, because they can be manipulated in a predictable fashion. Unfortunately, the same idiots that run the left also run the right.
Another reason not to vote is that it creates real despair among the small number of Democracy-shepherds. If you harm their ability to drive votes in a measurable way, you can blow up their careers. These types are numbered in the mere hundreds and thousands: they can be disabled much more simply than enormous populations can be.
So, don’t vote. Save your time. Save your money. Focus on preparing for the future, instead. Be willing to cede territory so that you can take it back later.