Embedded systems don't really scale the same way backend systems do. In embedded, you write the firmware, and it gets loaded into thousands or millions of devices. There may be a few updates, but firmware kind of gets frozen in time.
With backend, you write code that can be used to expand a business. You're adding features to grow marketshare or scaling up to meet user demand, so it has a more direct correlation with the health of a business. It's less of a cost center, and more of an investment.
Just as an example, in Vancouver, I got poached by a recruiter from G&E to work with FPGA in a senior position. The offer was around 80K.
At London a senior embedded systems engineer would get 40-45k pounds.
A senior fullstack / devops / backend dev at any of those cities can clear around 50% more easily with 10 times more jobs available to pick from.