Earlier quoted context omitted.
Because safari will sooner or later become another Edge. Apple doesn't invest enough into safari and now it's a browser which is most behind in terms of technologies.
Apple's Safari investment is focused on features like tracking prevention and anti-fingerprinting. Stuff for users at the expense of developers.
It doesn't matter how nice the privacy features are, when a user encounters web site after web site that doesn't work right in their browser, they eventually each out to a more technical friend that recommends trying browser X. When browser X fixes their problems, they never return.