The current system doesn't allow any other candidate other than those from the Democratic or Republican parties to thrive or even be known unless you're into politics, which most people are not.
Throwing your vote into a party you support, even if it isn't one of the main two, is nice and all. but that vote literally means **** cause it's below 1% that anyone other than a republican/democratic nominee will get any coverage and have their names thrown out there. The beginning is always about having your name out there so people recognize it.
So, when people say that they're just going to vote for one of the main parties instead of one that they fully support, it's normal because that's how the system works. Telling people who care very little about politics to do what you're saying instead of telling them reform is needed, is disheartening. "your vote matters" is a lie. It doesn't unless if it's for one of the two major parties who have twisted and corrupted the system.
tl;dr Your vote matters=You'll use the pythagorean theorem in life all the time.