You think that /k/ sounds like /g/, because you speak a language (English) that doesn't distinguish them. However, I imagine that writing "k" for /k/ makes perfect sense to speakers of languages that have /g/, /k/, and /kh/.
And your solution works for /k/ and /kh/, but runs into problems when you have a three-way contrast (/b/p/ph/ and /d/t/th). You can't write "buu" for "crab" just because you think it sounds like an English "b"; you need "b" for the actual /b/ sound.
And your solution works for /k/ and /kh/, but runs into problems when you have a three-way contrast (/b/p/ph/ and /d/t/th). You can't write "buu" for "crab" just because you think it sounds like an English "b"; you need "b" for the actual /b/ sound.