Having been a webmaster for a GM product information site, and done a fair bit of development, it IS a full time job to keep even the most basic type going, much less an e-commerce site that takes credit cards and deals with variable inventory levels. There is not enough money in the game to keep a maintenance person on the job AND do all the other work of casting, keeping lights on, etc.
It wass more work to deal with backorders and make the devils choices about which parts and which orders to prioritize than it is to plan out say X number of products, stack them, and let the market take it from there. It was common for a new part to go into the site, then have a mold break down and orders pile up while scrambling to retool. Thus, either cast to order or get out of the game.
Drag City hit this wall a while ago, and dropped their site in favor of a FB page. MLRC got sniped on the domain name, and after years of paying out to unreliable vendors just shut it down. FB is no prize, and seemed to do everything they could to find ways to extract revenue, and in the meantime interfered with our ability to just simply do a little business.
3D guys have it slightly easier - as long as the printer is working and properly fed, they can press the button and the parts materialize. More printing services will emerge over time as it becomes a bigger part of the hobby. Shapeways could own it if their search was not impenetrable; printing could be driving a lot of business for an LHS, developing that side hustle would be priority #1.