I'm no specialist but I believe some mathematicians insist on a so-called 'constructionist' approach to theoretical concepts. So I can sympathise with the idea that if we had to construct the set of Integers prior to being allowed to say anything about it then any talk of a set without a beginning might be ruled out. It seems true that no one human could construct the whole set of Integers starting from infinity, or starting from a non-existent beginning. You'd have to start from some arbitrary integer accepted as such, say -45010045648, or -1 if you prefer, and then count backward to get more negative integers.
Well, does it work though?
The idea would be that you could count backward up to any integer you'd be interested in. But, is that even possible? I'd say that however fast you would count those integers, there will always be at least one integer beyond your current capabilities, and obviously all integers beyond this one too. So, in practical terms, all human beings will ever be able to achieve would be a finite subset of the infinite set of Integers. Which means mathematics would have to be amputated from an entire section of studies. So, a constructionist approach will fail to produce the set of Integers as we envision it, with no good reason. So, why should we indulge the constructionist view (if that's what it is) at all?
And if we disregard the constructionist view, then there's no cogent reason to insist on saying that the beginning of the set of the negative Integer is -1 for example.
We could change our custom in this respect but I guess we follow the pattern that a finite set will be said to begin at its smallest integer and end at its biggest one, not some arbitrary value like -1. And so, naturally, an infinite past is said to have no beginning and to have an end, namely the present time. Big deal.
Some people here apparently think that's no way to talk. But that's definitely the way most people, in fact probably nearly everybody who has a modicum of expertise, will talk. And no good reason for changing our custom in this respect since no cogent argument for doing so has been presented, in all of 122 pages!
EB