It's interesting to notice that when Linux installs, most of them ask if you want to install alongside your other OS, and when they replace the boot loader, they replace it with something that allows you to access your previously installed OSes if still present.
On the other hand, we have Microsoft Windows. Which doesn't seem to know what "other OS" is, and when it overwrites your boot loader, it overwrites it with something that can only see WIndows and will only let you boot to Windows.
What I'm wondering is how that latter behavior hasn't been caught on to as a way to squelch competition? Yeah, maybe it's not as common as pasting icons all over people's desktops, but when someone is trying to flip between OSes, and one of those OSes is actively trying to prevent that and interfere with that, shouldn't it be a serious issue?