For those with older MacBook's or Mac mini's that used conventional 2.5 inch SATA notebook drives, a very affordable 2.5" SATA to mSATA adapter can be used to retrofit a mSATA card to a standard laptop drive form.
There are also Apple users who might want to explore mSATA based SSD backup drives for their OSX setup. Ready made storage solutions often referred to as 'Pocket Drives' can be bought in a variety of standard 128GB / 256GB / 512GB / 1TB capacities. They can be used formatted as-is for cross-platform PC/Mac use - or reformatted in Apple's disk utility for optimal use strictly on Macintosh systems.
You might want to cobble together your own mSATA Mac backup drive using any number of USB 3.0 or USB 3.1 Type-C interface mSATA module drive enclosures available for only $10-$20. Note, make sure 'UASP' protocol is supported in the enclosure to insure your solid-state Apple mSATA based backup drive performs optimally and gets the best data transfer rates possible.
Face it, the average consumer doesn't necessarily have the skills, the tools, or the nerve to perform their own Mac SSD upgrade. On some models it's actually quite trivial, takes only a few minutes and doesn't require much in the way of tech skills. You just need straightforward, step-by-step instructions. Other Mac models, even I wouldn't attempt. Some require quite a bit of disassembly before you can even physically get to the internal (usually) hard drive to even make the swap.
With the miniaturization of so many computer components, the connectors are ever more delicate, the screws insanely short and tiny, and often special driver bits are needed as more unusual star, tri-lobe and torx screw heads are used. It can make take-apart's quite challenging and nerve-wracking. No thanks!
For some, an SSD that's built-in or a Build-To-Order option on their NEXT MacBook or Mac desktop system is the way to go. I've pondered upgrading my 2012 MacBook Air's SSD from 64GB to 128GB for much needed elbow room. But this 4 year old laptop is getting tired, the keyboard is worn and getting unreliable and it's just smarter to look forward than to try to teach this old dog any new tricks.