Disclosure: I work at Microsoft.
Laptops, PCs are historically not, they are expected to be installed and customized, and were NOT designed for a particular OS, but work as "general purpose computing" (the universality of x86 in most cases).
There's no slippery slope, it's the customers want their general purpose device to be general.
Both deserve to be criticized for the same unethical practices. Android phone manufacturers may be the worst offenders of all.
If you don't want to pay the windows tax, don't buy the computer. They don't have any obligation to you unbundle hardware and software. Likewise, you have no obligation to buy it. It is a voluntary exchange.
After all, a vendor who is confident in the value of their product has nothing to fear in the face of fair competition.