That's your choice[1]. Some people sell upon vesting, and others liquidate periodically or to make down payments on property or health emergencies instead of going into debt. I suppose if one had a rainy day fund and the value of their RSUs doubled over one year, they may be tempted to spend the emergency fund since their net worth has gone up.

That said, I suspect you holding onto RSUs means you end up not saving as much for an emergency from your checking account, so you get an extra bit of liquidity.

1. I held onto RSUs too until I realized its indistinguishable from being paid extra cash and choosing to buy shares in my employer. I prefer rebalancing my portfolio with my preferred diversification mix.