It cost RAM to have a screen editor. A line editing routine is compact, saves a lot of bytes over making something that can scroll, copy-paste etc. The point of

It cost RAM to have a screen editor. A line editing routine is compact, saves a lot of bytes over making something that can scroll, copy-paste etc. The point of a built-in BASIC was that it was complete as-is and could run programs instantly. Thus while many languages for microcomputers used a batch compilation model and could do away with bookkeeping, BASIC was always slimmed to hit a nice small size and leave more room for user code.