The substantive question is, why do covered writes on brkb vs very liquid spy?

Certainly the premiums on BRK options are usually pretty low, so it's frequently not worthwhile to write them.
But, as for the question about "why not SPY", the risk/reward profile of single stock options is quite different from the risk/reward of the index.
Not to mention that they might have quite different valuation levels, meaning a person might reasonably have very different return expectations.

More interestingly, the risk/reward of an option on the index (or SPY) is quite different from that of the weighted collection of options on all stocks within it.
Even when you adjust for the greater observed volatility of individual stocks.
I presume it's because it's a very different population of option traders, with very different fear and hedging and greed goals in mind.

Jim