Right now the market seems to be in fluctuation within specific limits. This is sign for a bullish move, and that makes people keep hold than spending. This can be a reason why there is not much of spending compared to other cryptocurrencies through bitpay.
As said the service cost through bitpay seems high. Though it is a popular service provider, more applications have existed to perform the service on the regional way. Here in my country Krypto a new one have got developed and has slowly growing providing similar service.
With how bearish the market has been lately, it's probable people are holding more Bitcoin than what they're spending. I think the main reason why Bitcoin transactions are declining on Bitpay it's because of its processing fees. Merchants are considering other options in order to get more bang for their buck. With KYC requirements, you can bet most merchants and customers will be looking elsewhere. What really tells us if Bitcoin's payments are declining, is the network activity. So far, the blockchain is quite active compared to other cryptocurrencies on the market.
Slowly but surely, adoption is growing for Bitcoin's Lightning Network. It shouldn't be long before the whole world adopts Bitcoin for true financial revolution. As long as the main blockchain network remains decentralized, nothing else matters. Just my opinion