It's not an addon, it's extensions for services like klarna and zip that let you pay for things over time. Those 2 for example have apps that I can and do use but if I want to use them to pay for say concert tickets it's easier to have it all on my big screen so I can look at whats available and then copy and paste the number into the checkout.
It's not life or death and I can live without it. It is however the only reason I use chrome on my desktop these days.
That's good to know. I'm surprised that the 2 I currently have to use chrome for aren't already on FF. As I said, I should probably send them an email and ask them to launch one for FF.