The 2600 actually did have a BASIC interpreter cartridge available. It was both an incredible engineering feat (interpreter and IDE in 4K ROM and 64 bytes of RAM) and completely useless (because your program only had the other 64 bytes of RAM).
64 bytes is quite a lot if you use it cleverly enough. Sure, it's not enough for media but it's plenty to implement control loops and algorithms... Unless your code had to share that 64 bytes too, I guess.
