There seems to be some misconception about what IDPA competitors use and why. My experience tells me there are three types of folks shooting IDPA at Level 1 - 3 Matches.
You have about 25% of the shooters who are truly "competitive" types. They go from Master Class to Marksman. I'm not talking about sponsored shooters now. Of the 25% shooting SSP/ESP/CDP you will find top end 1911's, G34's, & M&P Pros and variants along with any of the latest PPQ Matches, CZ Shadows, and various iterations of the 320.
The 2nd and largest group (50% US) are the club shooters who enjoy the competition, buy whatever toys they can afford that either mimic the "competition" crowd or what caught their eye, seldom really practice, enjoy the fellowship and chase each others scores with enthusiasm. This makes up about 75% of shooters in Canada, maybe more. Few know the rules beyond the basic shooting rules and learn those 3 seconds at a time and truly enjoy themselves.
Lastly, in the US, you will find the "shoot what they carry" group. They often use IWB holster, leather or kydex, wear anything from grand.dads button shirt to some form of shooting vest. They test themselves using what they would use to defend themselves at matches In this group Sig 226, M&P FS, Sig 320, CZ 10C Beretta 92FS would be as common as 75 Pre B's, G17's and 19's in SSP I have seen revolvers out of leather as well in revolver division.
Level 4 and 5 Matches tend to be populated by the Pros and the truly competition crowd. It cost money to travel to the US Nationals or World Shoots. The shooters that go there are in it for the competition and for the most part know what the rules allow, are talented or come for the experience and enjoy their week of shooting. There are lots of clubs types as well but fewer with the cost of travel being what it is.