Why are canon nikon cameras so similar?

Thet will never pass a blindfold test, except by a proficient photographer with adaquate experience.

For the past few years, i've explored so many different systems, and image formats. The results and challenges i've been able to overcome has been an amazing experience. I've learned more with the various format film cameras than i could possibly learn with a digital camera(in a lifetime).

Cameras include,
Pinhole, rangefinders, slrs, dslrs, tlrs, lfs i.e. 4x5.
I've been using the same film almost exclusively. Ilford hp5. 135, 120, 4x5 sheet film.
Learned so much with these cameras and film.

Why don't canon and nikon expand their camera line and offer a number of different cameras. Each with their advantages and disadvantages. Let this help photographers see the world a little differently with each new camera they offer.

Because developing a new camera costs money and they want to recoup that by selling a lot of them.

It's not just Canon and Nikon per se. The problem is that you already know photography hence you find using any camera simple as pie. Digital cameras offer little new from where film left off. It took so many decades for film to reach its peak. Digital, already a few decades old is still relatively new.

HDR (better executed through the computer though) and panoramic scans (like in slapping a scanner behind a large format camera) are some of the new things digital has to offer. We can be sure there are more to follow. Casualties of this advancement, pictures will get bigger while cameras will get smaller. Hopefully, it will be more than those two.

Fundamentally the overall features reuired by a camera dictate the design. They all need detachable lens, shutter release, controls to change settings, a firm handgrip, etc etc

Just like all cars have 4 wheels, engine gearbox, steering wheel, pedals etc.

It was ever thus! Tthe DSLRs of today have only changed a small amount from the first SLRs of the 1950's.