it would be one thing if dishonest employees simply underperformed, but they also often suck up other people's time.
It sucks being a manager and pumping tons of time trying to get someone up to speed and not knowing if they just need more investment and support that will pay off or if they aren't reciprocating effort and working other jobs.
After being burned, my default is little compassion and investment in full remote employees. Ill train in office employees because I have more confidence I'm not wasting my time.
This is on top of the fact that multiple employment usually requires directly lying to your manager and coworkers, inflating task difficulty, or creating problems for others to slow the overall pace of a project.