That's not quite the reason. The system is setup to vote on individuals. The idea of voting for party is propaganda from the parties. Third party candidates in the modern system tend to fare poorly because the districts have been made unmanageably large and require multi million dollar advertising budgets. Which is money that comes from the party and party endorsed fundraising.
Money. They wouldn't be able to fundraise the money they need to get messages out to people. Then there's the depressingly large number of Americans who vote by party in a system meant for voting by individual. They would lose funding and then get smashed in the elections because nobody knew the party was even there.
Not just when they lose. If you have a fully successful president that does both terms they also then fuck off to obscurity. They aren't unpopular among their base, they just retire.
How do you think they're going to transfer the money on a more mature coin? Oops, we lost the keys.
Oh look Putin and Thiel randomly managed to find the keys to America's Bitcoins.