Leaving the property empty can be worthwhile if you make more from the capital-gains than you would from {rental income, minus repairing problems caused by the tenants, minus maintenance, minus property management fees, minus income tax}.
Don't you make the same gains on the property regardless of if its rented or not? You might not need the money from renting it but its still going to be more money above the gains from appreciation...
You can't time the market and sell the house if there's a tenant living in it. (I'm guessing that's the thought process)
Yes but the whole point is that that's only "worthwhile" for you, and it contributes to fucking everyone else in the housing market over.