Every language has things like this that seem weird to a non-native. As you learn languages, you'll find it's helpful to keep a category in your head (or a list somewhere) of: "That's Just The Way It Is." Why don't most Chinese verbs conjugate to indicate time? Answer: That's just the way it is. Why do romance languages have two verbs for "to be", and four ways of saying "to be" in the past tense? (está, é, estivesse, era - Portugûes) Answer: That's just the way it is. Why does ANY language have gender? Who cares if an apple is feminine (la manzana) or if a plane is masculine (el avión) (Español). I'm going to eat the apple, not marry it. Answer: That's just the way it is. Why does English require that you "chop DOWN" a tree, before you "chop it UP"? Answer: That's just the way it is. It's ultimately a sign of how infinitely inventive the human mind can be to describe the infinite realty that we confront every day. :o)

Useful little word, isn't it? Yes, "It's got a good radio ..." is using a contracted form of "it has". It's true that "have got" in your that and your preceding examples can be seen as redundant with plain "have", but the "got" is quite colloquial (especially in UK English) and serves to emphasise the possession or compulsion. (Note that you can only use it this way in the present tense; you can't say "I had got to go" or "It will have got a radio".)

A few decades ago, using "got" was considered improper English. Nowadays, not so much. This is still incorrect grammar: - it's got a radio / it has got a radio (= it has a radio) As a substitute for "must / need to / have to" it is correct grammar, but should only be used in casual speech: - it's got to have a radio / it has got to have a radio (= it must have a radio / it needs to have a radio / it has to have a radio) There are many, many fixed phrases with "to get", which are completely natural in speech, but should be avoided in writing because they still "sound" too casual: - It's getting cold outside. (becoming) - I got out of the assignment. (avoided) - I get paid weekly. (am) - Get out of here! (leave) - I've got to get out of here. (must leave) In North America, the past participle is "gotten" and elsewhere it's "got": - It has gotten colder the past week in Chicago. - It has got colder the past week in Sydney.

Past and past participle of get.

Well, its probably due the way English has progressed throughout the years. Its just an informal way of speaking. So yes, like you said, its also for our own comforts as well.