So why would a covered call strategy have such a relatively low yield?
I'm guessing here, but I would hazard a guess that shorters are using the Calls as insurance against a margin call on their short positions. See that latest from Andrea Kramer here.
Most notably, the stock's deep out-of-the-money May 65 call has seen about 750 contracts change hands at a volume-weighted average price (VWAP) of $0.78. Ninety percent of the contracts traded on the ask side, and implied volatility was last seen 4.1 percentage points higher, hinting at buy-to-open activity. ... By purchasing calls, the shorts can lock in an acceptable price at which to repurchase their shares, should TSLA skyrocket in the near term.