Yeah, I remember around 1990 or so, everyone was going to bike shops looking for that magical "$300 mountain bike". Manufacturers obliged, and the rest is history. One of the worst casualties of this was that road bike manufacturers decided to limit tire clearance to 25 mm, in the hopes that anyone wanting to use a wider tire occasionally would need to buy two bikes instead of just one.
Every non-cyclist had to have an MTB (dammit!) as a way of getting into riding, without being too "extreme". You could sit upright like in an office chair, with a big soft seat and upright handlebars with long brake levers. Early MTB's often weighed 35 lbs, but that was not a problem since few ever went off the road (intentionally). Walmart has now pretty much conquered this demographic these days, and the "$300 MTB" now costs around $200, but it still weighs 35 lbs.