Bitcoins can exist without exchanges, but would you support the argument that the existence of exchanges are among the factors facilitating the popularity and accessibility that people have to bitcoins?
I would agree. Bitcoin in itself no matter how popular it may be wouldn't come this far in utilization if exchanges did not exist. They are the ones who made bitcoin and other cryptocurrencies completely accessible and transactable. I would argue however on the matter that exchanges are the ones that made bitcoin popular. Even in its early days bitcoin is already being talked about by many, and it grew popularity on its own, without any outside help from a third-party entity or whatever. Bitcoin made its name for itself, while exchanges made sure its popularity is reached through multiple facets by many people. It's a mutual symbiosis between the two really.