Ohh now when you say that about modifying them, I can see that too – with RGB and HSB, you can use variables in each of the 3 channels and change them mathematically.
HEX uses a different base too (we use decimal base, based on ten, but HEX uses hexadecimal base, based on sixteen.)
And HEX is basically the same as RGB. But I can see what people mean about using converters, particularly if you have a lot of colours. I was thinking about suggesting using colour pickers that have HSB or RGB equivalents, but I also use some colour resources that have the colours in HEX – although I don't find it too much of a bother to convert hehe but I can understand.