[IncPen]

I’d wager that a big reason for the laggards is that they make hardware that won’t die. I know many with 7 or 8 or 9 year old macs who see no reason to upgrade; email and internet work fine on their old machines.

[CarmichaelPatriot]

Some of those older Macs don’t support the latest versions of OS X. If Apple would put out a 64 bit EFI for the Mac Pro 1,1 2,1 and 3,1 plus the iMacs and Mac Minis that could support it, they might pull as many as half of the users up to Yosemite.

Why should they replace a machine that still functions well for them, especially when you consider the high cost of Apple Macs?

[roadcat]

I know many with 7 or 8 or 9 year old macs who see no reason to upgrade

For instance my wife and her 2006 Macbook. It's maxed at OSX 10.7.5 Lion, can't go higher. She's fine with it as is, except for not being able to access iCloud streaming photos from family; she runs to my Mac Mini running with Yosemite. I was worried about upgrading my Mini after hearing grumbling from some, as I didn't want to lose use of my Adobe Photoshop suite, but they work fine on Yosemite and I haven't encountered any problems. I have a number of older Macs with varying OS versions. The hardware works fine, no reason to stop using it unless you need newer hardware for newer apps and speed.

Reason for some laggards is because you can't put newer OS versions on them due to hardware limitations.

[BradyLS]

That’s the other shoe dropping, for sure. The Macs have at least double the half-life of the PCs in that company.

[martin_fierro]

I have an old G4 eMac that is

l a   g      g        i            n                 g

Speed-up tips appreciated