[kps]

Historically, a few were included in the Letterlike Symbols block¹ because they were present in some pre-Unicode character set. Much later it was argued that since a few were present, they all should be present.

¹ https://en.wikipedia.org/wiki/Letterlike_Symbols

[chungy]

Also note that these selective ones were part of the basic multilingual plane, where space was always a bit at a premium. They were assigned before Unicode expanded to have 17 complete 16-bit planes and space stopped being a problem.