No. Many countries, including the US (most of the time), have rules that require passengers to pick up their baggage when connecting from an international flight. Some airports may not be set up to enable this type of transfer for all connections. Other policies may apply - e.g. airports or security agencies may not allow airlines to hold baggage more than a certain amount of time. And airlines may set limits on how long they're willing to hold baggage. There are lots of reasons why a customer might be required to pick up their baggage at a connecting airport.
We've had
many threads here over the years asking about whether or not AC would hold bags on long layovers, including overnight, and there's now
a consolidated thread with detailed information. Putting my moderator hat on, I'll ask that discussion on that point move to that thread to keep this focused on the voluntary change question.
The question is not why did AC "make" your connection that way, it's why did you choose to book it? We don't know when you booked the ticket and what the schedule was at the time. It's possible the YUL-MCO evening flight wasn't on the schedule at the time, or that the timing of the flights was such that it would not have been a legal connection. It's also possible that this option
was offered and that you chose to book the overnight layover because it was significantly cheaper (if the price difference was high, and price was your main focus, you may not even have noticed that the same-day option was available). Regardless, either you chose to book the ticket this way, or at some point a schedule change occurred that would have allowed you to move to something different, and you chose not to take it.
If you're now unenthused with the prospect of an overnight connection and possibly having to re-check bags, I encourage you to contact AC (or your TA, if you booked through one) to find out the cost to change the ticket to a same-day connection. You can ask not just about changing to the YUL-MCO flight the night before, but also look at changing the route altogether, e.g. perhaps connecting in YYZ instead of YUL. There's a decent chance, though, that you're not going to like the cost: as [MENTION=10124523]lc246[/MENTION] said in the very first reply, you'll have to pay the fare difference, if any, and likely a change fee as well.