[compumike]

This is an issue we've been tackling at CircuitLab (https://www.circuitlab.com/), and the fundamental issue is that the chip makers (Linear, TI, Analog Devices, etc) don't want to let their device models out of the building. They often do have simplified models for simpler parts (op-amps), but for more complex mixed-mode parts (switchers), coverage is sparse, and a SPICE netlist is a poor language for encoding the control logic. LTspice, for example, includes encrypted models for many of their switching power supply parts, and those include special non-standard SPICE behavioral components to make the models possible to execute in a reasonable amount of time. Other companies with web-based / server-side simulation keep the models entirely opaque and tremendously limit your ability to configure the surrounding components. The goal is to get you just far enough to have confidence that their chip is the solution for you, and then get you to use their tools and field application engineers. This is the status quo and they're generally not in any rush to disturb it.