I come back again to asking why the Atari is so much easier to program than anything else, and I am reminded of why I was frustrated with programming the TI-84+: there's no easy way to program it on the device. Aside from Atari's assembler, Machine Language for Beginners came with a short-but-useful assembler written in BASIC, that lets you write small programs and get a feel for the processor. You can literally write a small, 6-instruction program, assemble it to a safe memory location, and execute it right there, then give control straight back to BASIC. So, let's say you want to play with the arithmetic functions, you can write a little program, save its output to memory, and then PEEK it back in BASIC.

On the TI calculators, well, you'd have to write the program on you computer, transfer it to the device, execute it, and heck I don't even know if there's an equivalent to PEEK and POKE on the thing. So you'd also have to write code that outputs your little test data to the screen in some fashion. The barrier to entry is a lot higher.

Same with coding on the DS, since it doesn't have a flexible runtime environment. You have to write quite a bit of complex code just to play with the thing. It's easier when you're piggybacking off of DevKitPro, but that obfuscates the hardware away and it's harder to see what you're actually doing.

I suspect this is also why Python is such a beginner-friendly language, since it has an interactive interpreter. You can play with functions before working them into formalized programs.

So yeah, BASIC is a pretty limited system by today's standards, but it gets the job done if you know what you're doing.