What better alternatives are there?

“Smart” boards — expensive, and high drawing latency makes writing on them uncomfortable. Also, text is hard to read from a distance. (They may be better for accessibility.)

Dry-erase boards — boards and markers are expensive. Markers generate a lot of waste.

Chalk — cheap, naturally occurring (and safe to dispose of) material. Easy to read at long distances.

You're probably thinking of green boards when you say chalk boards because black slate chalk boards are a pleasure to draw on.

If you have ever used one, you'd know they keep using them because they prefer it.

They are also easier to read from a distance compared to a dry-erase board.

Having used said chalkboards there - they are amazing. The chalk is really smooth to write with, and the tactile sense is much better to draw on than a white board.

The most amazing thing though, is that person or persons unknown goes round and cleans the boards at the end of every day. Even in the holidays.

Still the best solution for teaching complicated topics that have a compact notation.