In the end, integers, floating point numbers, "text\n", emojis etc. are just sequences of bytes. You choose to acknowledge it and take advantage of it, or you don't.
A bit late, but bytes are very often the smallest addressable unit. That's why they are "special".
Which answers your second question: "bitstreams" would be terrible because they are not well connected with a hardware reality. Unless you have bitstream-oriented CPU, it is a bad idea for a basic type to go against the hardware.
Why even have types... Well, yes, there are languages without type checking where the notion still exists. For instance Forth has no type checking but two types are implied: the "byte" type and the "machine word size" type, maybe three if you count strings.