Ever since flash drives (USB sticks) were invented, people wondered if they could run their OS on them. The answer was "no" because the number of writes required by an OS would quickly wear out the flash drive.
As SSD's became popular, wear-leveling technologies were improved in order to allow operating systems to run on them.
Various tablets, netbooks, and other slim computers use flash memory instead of a hard drive or SSD, and the OS is stored on it. How did this suddenly become practical? For example, do they typically implement wear-leveling technologies?
Best Answer
TLDR: They finally became cost effective for mainstream use.
That wear's the only concern is a bit of an assumption. There have been systems running off solid state memory for a considerable period of time - many folks who built car-puters booted off CF cards (which were electrically compatible with PATA - and trivial to install instead of a PATA hard drive), and industrial PCs have had small, rugged, flash based storage. That said, there wasn't many options for the average person. You could buy a pricy CF card and an adaptor for a laptop, or find a tiny, very pricy industrial disk on module unit for a desktop. They weren't very large compared to contemporary hard drives (modern IDE DOMs top out at 8gb or 16gb I think). Pretty sure you could have gotten solid state system drives set up way before 'standard' SSDs became common
There have not really been any universal/magical improvements in wear levelling as far as I know. There have been incremental improvements (while we've been moving away from pricy SLC to MLC, TLC and even QLC, and smaller process sizes, all of which lower cost, at some higher risk of wearing out). Flash has gotten a lot cheaper.
There were also a few alternatives that didn't have wear issues - for example running the entire system off a ROM (which arguably is solid state storage ), battery backed ram, which many early SSDs and portable devices like the palm pilot used. None of these are common today. Hard drives rocked compared to say, battery backed ram (too expensive), early solid state devices (somewhat pricy), or peasants with flags (never caught on, terrible data density). Even modern flash memory is a descendant of fast-erasing eeproms), and eeproms have been used in electronic devices for storage of things like firmware for ages.
Hard drives simply were at a nice intersection of high volume (which is important!), low(ish) cost and relatively sufficient storage.
The reason you find emmcs in modern, low end PCs is the components are relatively cheap, large enough (for desktop OSes) at that cost, and share commonality with cellphone components, so are produced in bulk with a standard interface. They also give great density of storage for their volume. Considering many of these machines have a paltry 32 or 64gb drive, on par with hard drives from the better part of a decade ago, they're a sensible option in this role.
We're finally reaching the point where you can store a reasonable amount of memory affordably and with reasonable speeds on emmcs and flash, which is why people go for them.