The problems are not specific to SQL though - if you want to store and manage huge amounts of data you're going to need some specialized data structures, some way to manage disks paging and memory, manage consistency, isolation, durability, and atomicity of your changes.
The general idea is that its such a PITA to deal with all that so just let a database do it, and of course the consequence is an often leaky abstraction because computers suck.
It's more than a PITA, it's almost impossible to implement ACID correctly. It's very very hard to do. There almost no point in implementing that in house when we have sqlite3.
The general idea is that its such a PITA to deal with all that so just let a database do it, and of course the consequence is an often leaky abstraction because computers suck.