Can't upvote this enough.
I support an Open web, I test my websites on Firefox and Chrome, I even occasionally do Edge testing, and I develop my websites often primarily in Firefox. But I'm not buying an iPhone or a laptop just to test websites, so I don't test in Safari.
Every other browser has a way to emulate in Linux, I can even download free VMs from Microsoft to test IE11 in Windows (and Edge now runs in Linux). If Apple isn't willing to make its operating system available to me to test on then I don't see why I should feel obligated to test on it.
And given that there is some Mac-specific behavior for Safari/Firefox that I've run into (differences in how blur works), and I generally can't assume that all of my stuff is going to work perfectly, I'm either going to fall back on progressive enhancement or (in the case of a complicated webapp) I'm going to tell users that Safari is unsupported and they're continuing at their own risk.
I'd love to support Safari. All Apple has to do is give me a way to.