I feel first party strobes (either Canon, Nikon, Sony, etc) are a very VERY narrow market; event and party photographers (which uses on camera flash the most) usually look at their wallet, and buy cheapest stuff they can find, because they know they will bash the thing around quite hard and get beers and drinks spilled on it, so they're not going for uber expensive first party stuff.
And when you switch to off camera flash and/or multi strobes setups, you definitely look at standandalone strobes with a system around them, so Godox, Wescott and similar if you're in a low/medium budget, or Profoto if you0re on a high budget or you rent (or Elinchrom or Broncolor; but I don't know if they have small and portable battery powered heads like Profoto has). First party strobes really don't work for off camera flash, they don't have a fully developed system around them, and they're not brand-neutral (except for the trigger) when you change system, either because you switch or simply because you run two systems in parallel (I know many with CaNiSo FF kits and a lighter Fuji Aps kit).
Photography is less "popular" then 15/20 years ago, there are not many advanced amateurs anymore, which were the people who most used first party strobes.
Now we just remained with basic "smartphone" amateurs, who buys R50/R100 and equivalents from other brands, and would rarely, if ever, attach anything on the hot shoe.
There are working professionals, that buys into strobe systems, and first party strobes don't have any system around them, and they are too expensive anyway; if they run small business they buy Godox, if they run medium business they buy Profoto/Broncolor/Elinchrom (maybe not the latest stuff), and if they run big business they don't buy as they directly rent when needed.
So who buys first party stuff? Rich pro? Yes, maybe they buy some and they get them to some use, but numbers are small. Rich amateurs? Same, they're small numbers.
With a Canon EL-1's price (but is the same for the Profoto A1) you buy two Godox AD600BM studio heads with good stands and a couple of sofboxes, or three super flexible AD200Pro with the same accessories. Someone is certainly buying the EL-1 or the A1, but I don't think numbers are enough to justify them, at least for Canon and the other camera manufactures. Let's have them do cameras and lenses, and leave stobes to strobes manufacturers.