Genealogies are given to establish the legitimacy of a people, a particular ethnic group; that the people are descended from the originator(s) of that ethnic group. They were a way of establishing the roots/origin of an ethnic group. In royal genealogies, they are also a way to establish the legitimacy of the current ruler.
You see this a lot in “kings lists” right down to the Middle Ages – it was common practice to trace a given king’s lineage all the way to Adam and Eve to establish his god given right to rule (and be king).
Some will use them to reckon time (relatively speaking) – the idea here is that there was no established “year one and we start counting from here”. Israel was not established as a nation yet so regnal dating couldn’t be used. People had to have a way of reckoning their own history and counting generations was the easiest way. Using the lists of genealogies to try and reckon time presents a number of problems. Obviously there are a ton of gaps and missing years, so fantastical ages were given to some of the individuals – where that happens is where the gaps are. It’s easier then filling in with a bunch of “unknown” generations.
In addition, the concept of "A begat B" doesn’t always imply direct parentage – a better way of looking at 'begat' would be “begat in the line culminating in..” The terms 'son' and 'father' can mean 'descendant' and 'ancestor' as well.
As others have mentioned some of the individuals in a given line have some interesting stories associated with them.
Being an avid genealogist, I can appreciate the genealogies given, but as far as ages and dating goes - that's more a secondary purpose and can't really be relied on with any degree of accuracy.
But, yeah, they are long lists!
"Bunni", by the way comes from the Hebrew root 'bana' - to build, so presumably our guy Bunni was named after his profession (like Mason, Tanner, Smith, etc.)