Those Bulb Flashes were expensive!!! I remember as a kid being excited to find packs of AG-3B marked down to 29cents or so, evidently no one realized they would work in an Instamatic 150. M3 flashes- Expensive, used them in the Polaroid 104. Being able to buy an electronic flash for $16 or so saved a lot of money. Also- Sync speed was 1/30th for M Sync, X-Sync at any speed. The HM9 also has 1sec and 1/2sec shutter speed, also would require a bigger mechanism. I'm trying to remember if I have a 7s in the closet- several people would send boxes of non-working cameras as "payment" for fixing some of them. Picked up a lot of cameras that way, had good luck repairing 75% or so.
I've not used a flash on a 35mm or Digital RF/SLR in a long time. Flash on my Polaroid SLR690 and SLR680 (Retrospekt rebuilt)- yes.
This is taken about 20 years ago, with my Contax IIIa and 1934 5cm F2 Sonnar. C41 B&W, ISO 400. Window light. I converted this lens to Leica mount about 15 years ago. The Contax IIIa has a 50/1.5 Zeiss Opton on it...
Note to self (invent time machine first) The HM9 is great wide-open, save the money on the Flash, buy faster film, open the drapes on the Picture Window in the Living Room.