I own a 2008 Mac Pro, and High Sierra isn't available for my machine. Why should I buy a new machine if my current one works just fine? Note: I need High Sierr

I own a 2008 Mac Pro, and High Sierra isn't available for my machine. Why should I buy a new machine if my current one works just fine? Note: I need High Sierra because I use this particular machine for music production, and the latest Logic Pro X requires High Sierra, and all of my collaborators have updated so I can't open tracks originated by them anymore.