Cartridges are and where very cool, but it is a fact that cassettes worked very well on the Enterprise, compared for example with tape loading on a Sinclair. I suffered it for years as my previous computer was one ZX Spectrum .
Even so, how much
Spectrum cartridges do you know?
Ok, it was not the same case as you needed an additional ZX Interface 2, but for the common user a tape offered more advantages than a cart. You could copy the game to a friend on a cheap cassette.... even modify it or add pokes...
For a user the real upgrade that far times was to have an Exdos card and be able to load a game in seconds instead of minutes. A box of floppys was more desirable than a cartridge, and cheaper(not counting the expensive interface...).
But that where only my thoughts, is adventurous to say why things had happened.
I understand you, cartridges are a concept, begin and end in their selves, closed boxes of fun.
Is for that I have emptied one of my two Basic cartridges to put inside my lovely SD-reader.....