In my experience writing tech history, the most common reason is money. The second most common reason is entering a crowded market with little differentiation. The second reason could have been solved by marketing, but many in the industry are allergic to marketing.

If you are building a better <insert product here>, this must be heavily and clearly marketed. Otherwise, people have zero reason to switch. Why mess with what's working?

Additionally, just being cheaper doesn't make a product better. If I were starting a new effort, the cheaper part might be enough. If I already have stuff in production, cheaper isn't sufficient.

Feel free to tell me I'm wrong, but these are my observations.