Well you are right, but I somehow don't like being forced to upgrade perfectly good machine(s) before their time
Well this is the part you missed -- that machine is PAST its time. Well past it, in fact. The fact that it is still working is great, don't get me wrong ... but it's much better to replace a machine while it is still working well than it is to wait until the day the hard drive dies or you're looking at an expensive repair to decide that you need a replacement machine, and RIGHT NOW.
Having an aging but working machine means you have some luxury of deciding when and what to replace it with, but as a rule of thumb: if your machine is so old it cannot support support the latest version of OS X, you should be replacing it within the next three years. Your machine hit that point in mid-2012, when Mountain Lion came out, so it should have been replaced sometime last year. This is little to do with planned obsolescence, and much more to do with changing Internet technology, increasing software and hardware capabilities, and most importantly SECURITY.
The whole thing sort of reminds me of when Adobe went from sending you a set of disks to charging you a monthly rental fee.
I was *super* resistant to the idea of subscription software at first, but you know what? I don't miss the days of shelling out $1,500 or more every other year for a new Adobe suite -- I'm kind of retired from graphic design work, but if I was running my own little shop I think $75 a month for only the months I needed it to have the ENTIRE (and much larger these days) latest Adobe CC suite is a very fair price (it's actually just $50/month on a yearly basis). Right now I'm just paying for Photoshop ($10/month) ... which previously sold for $700+. If you do the math, I'll have paid for a complete copy in just
seven years ... and had the latest version and full support of the product during that entire time ... just sayin'.