It only matters if you have the points for time you want not if you have the points on the day your booking them. Use year makes no difference.
Not with the banking rules. If everyone had a Jan use year and the eight month banking rule, meaning bank them by no later than Aug 31, there would be many who would be wary of booking a room for time in the fall because if anything happens to require cancellation of the trip, the points can be lost.
Over the years this site has been in existence (since the 90's), there have been many posts by newcomers asking for advice on the best use year to buy, and one of the answers given and repeated by many was that, if you have a particular time of the year you will likely go, buy a use year that begins not long before that desired time of year. Example: if you usually go in Nov, a Sep use year is a good one to have. Make a reservation for Nov that you then have to cancel and you will still have plenty of time to use the points for a different trip in the same use year or to bank them. If all were allowed only a Jan use year and one desired to book Dec all the time, then you would lose the points if you ever have to cancel.
The original banking rule when the use year months were created was that you could bank all your points by end of the sixth month of your use year, 50% by end of the ninth month and 25% by end of tenth. Those were not cumulative totals, e.g., if you banked 50% at the end of your sixth month, you could not bank anymore thereafter.
In other words, having many use years is ideal if you set up a system that allows banking while limiting the time by which such banking needs to occur. The combination of multiple use years, coupled with the banking rules, helps to spread out demand throughout the year.
Moreover, for many years after
DVC first went on sale, Disney was using the varied use years as an additional incentive for sales. New purchasers, if they did not choose a use year, were typically given one that started three to four months before the time of sale. The sales pitch included that you would have less less than a year to wait to have double the points you purchased.