Conventional synthesizers—or if you prefer, non-modular synthesizers—generally give you a fixed number of modules and a fixed audio path within which those modules are deployed. You may have some routing options—for instance, you may have a number of filters through which the sound can be directed, or you may have some modulation choices—but on the whole, the synthesizer is “fixed.” And that design of synthesizer is the most popular design.
This fixed-architecture approach is popular for a variety of reasons:
It’s fast. You don’t have to load up the modules—you just start crafting sounds.
It’s easy. You don’t have to hook up the modules.... (And, generally, the synthesizer will make a noise immediately.)
It’s straightforward ...