The ability to manage work-life balance when working remotely is a very rare ability, and one that takes practice to develop. The same ability is required of startup founders. Those who can define structure for themselves, even without external instruction, and then execute within that structure, will always succeed before those who cannot.
Because this ability is so rare, and necessarily present in startup founders, we can logically assume that a higher percentage of startup founders have the ability than the percentage of others who do. Or, at least we can assume that startup founders are the most well-practiced in this ability to execute within their own structure.
This means many of (not all!) the people who are best at managing work-life balance (a requirement for a productive remote employee), are already founding startups. So the best remote employees are selected out of the hiring pool if they decide to found startups instead. This leaves you with a plethora of less-competent potential remote employees, who are not as skilled at managing their own work-life balance as the best of them.
A risk when hiring a remote team is that you recruit too many employees who cannot properly manage their own work-life balance, and therefore suffer productivity losses. I would imagine the effect compounds as you hire more employees sharing this weakness.