In order to run your MC simulation, you'd need a model for your start-up's success. I have no idea how to do it, maybe there's something you could do with the funding part (simulate interest rates and something like that), but in the end you'd end up with a model that probably would not say much about reality. Then you'd run the simulations and get results that at best would be worthless and at worst harmful.

I don't know if VCs do it, but I'd hate to have the funding for my company blocked by some shitty model that I would have had to game in order to get the dollarybucks.

It depends on your niche.

If you are designing electronics, it might help you assess some extreme cases of your circuit designs.

But, if you are asking the question, most likely is because you don't need it. Because when you need it, you definitely know it!