Bitcoin works regardless of the price. There is nothing to worry about, even if it drops below $1.
Sure, it might still work but where is my $70,000 that i invested?
Good things investments don't have risk or otherwise that would be scary!
In all seriousness though, you invest and put in a lot of money you know where your 70,000$ is right now, its with an exchange and you no longer own it but you do own Xamount of Bitcoin and if its worth a penny it doesn't change how much bitcoin you have.