There are many instructions programmed inside such small microcontrollers, and with such a small size, the way SD cards handle data is quite rudimentary. It tends to store data anywhere and read it in the easiest order possible.
SSD cards are not so when they can put memory and the entire structure into a space that fits snugly on the computer's drive bay. Here is the picture.
Space of device processing on SSD card
The structure of the SSD is built to ensure that no element is used more than other elements, keeping the job with every file balanced. This is what you expect from a drive to read / write a lot.
Large space allows manufacturers to put buffer data storage chips, which are important when managing heavy and repetitive tasks. There is no wasted time and everything is very smooth.
In addition, the large size also consumes more heat, creating microcontrollers that need more power, which is impossible in SD format (because it needs more power than small devices can provide. and more heat emission.
Each type is designed to work on different environments. SD is best when used to store and playback files while SSD is optimized to run the computer operating system defragmentation and what the task requires. One side has a simple role while the other needs to be smarter, more adaptable. It's not just about speed, it's about flexibility and workflow.