Cgtrader provides Marmoset viewer embeds for interactive viewing of the models, but very few sellers are actually using them. There are several reasons for that - first, it requires to have Marmoset Toolbag program, which costs money. 2 - you have to spend extra time to prepare model for the viewer. 3 - not all models are suitable for interactive viewer. 4 - Cgtrader's implementation of Marmoset viewer is buggy and more often than not it is simply not working. 5 - Marmoset viewer is pretty insecure, it is relatively easy to rip models from this viewer.