Cost: eMMC is significantly cheaper to produce and integrate into motherboards. This allows manufacturers to hit the sub-$200 price point for laptops and tablets.
The "5.1" refers to the set by JEDEC (the industry body for solid-state technology). Version 5.1, introduced in 2015, brought several refinements over previous versions (like 5.0 or 4.5), including improved command queuing, background operation enhancements, and better write caching. In practical terms, eMMC 5.1 supports a theoretical maximum interface speed of up to 400 MB/s (using HS400 mode). While this is significantly slower than a SATA SSD (~550 MB/s) or an NVMe SSD (several GB/s), it is a major step up from older eMMC 4.x versions or spinning hard drives.
The chip is a single BGA package (often BGA153 ) soldered directly onto the device's motherboard, making it a permanent fixture.
If you already own or must use a device with this specification, survival strategies exist: