Why class A network addresses has a restraint of "not taking initial and final network address" , while other classes won't

Question

Since we know that class A has the range of its network address (first octet) from 1 to 126 , since we wouldn't choose 0 and 127 .. but in class B the range is from 128 till 191 ... in class B we are not removing first and last .... why is it so ... is loopback address only relevant to class A

Comments

@Infinity_love So by this observation can you say limited broadcast address only relevant to class E network  ? 

Answer 1

This is how it is defined 0 and 127 are special address.