Most of them use payment processors such as Bitpay and Coinbase and most of them don't actually receive any bitcoins but they receive the fiat equivalent of it. In other words the reasons why they do it is not because they want someone else to control their money but because they want to receive fiat not bitcoin which is because of its volatile price and the fear they have of sudden dumps.
These merchants accepts bitcoin payments through these payments processors who convert them directly to the legal cash of their country and it's ok as these traders need cash to run the business and Bitcoin is not widely accepted at the moment but they accept to have more customer base as this is the latest trends and both the parties are satisfied like customer pays with btc and the vendor gets fiat for the same.But they can also hold btc in their wallet and earn more profits over it as the main aim of btc is payment processing apart from asset and they don't need to fear it and hold it instead but with time they might become aware about it.Rest you have nice avatar for you which shows Btc at discount for December and those who can understand it will have bright future ahead.These discounts will be rare to see when you will be buying sats only with few dollars.
