Capacious and fast, low-power nand chips are much more expensive than mass-produced SSDs of the same capacity.
Moreover, the more capacious the disk, the higher the rest consumption. Same with RAM.
All external microSDs are much slower than built-in drives, and at the same time, the readers and they themselves consume significantly more than optimized and carefully selected built-in drives. This is why microSD slots are most often abandoned - they dramatically reduce battery life, especially if code and frequently used data structures are transferred to them.
Large RAM allows you to reduce intensive exchange with the disk and swap file. This leads to increased autonomy and the ability to simultaneously hold more software and data in memory, which increases the smoothness of operation and system response. But a large RAM capacity, as written above, also increases background consumption. This requires a carefully calculated correct balance from the developers.