system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why SSDs aren't better, if we have stuff like the Sandisk 128GB microSD

It was my impression that SSDs and microSDs both use the same technology, essentially.  So why can't SSDs be made bigger and cheaper, if 128GB fits onto something as small as my thumbnail?
gpt
First of all, microSD cards have no controller inside. They require an external processor to control everything, which is usually very simple. SSDs have very advanced processors inside which decide where to write information into the flash memory so as to avoid wearing out locations, as well as erasing information in an efficient manor. These processors and their interconnects take space. The big key though is speed. microSD cards can only be written to at 10-20MB/s whereas SSDs can be written at 500MB/s+. There is also the factor of Input/Output Operations per Second or IOPS. This is how many individual reads/writes can take place in one second. microSD cards may be up to 1000 IOPS, but SSDs can get up to 100,000 IOPS easily, mostly due to their onboard processor.

Basically we can make flash memory devices small, slow, and low durability, or large, fast, and high durability, the latter being more suited to SSDs.