The government is not the main reason, but we cannot deny the fact that they have in some way contributed to it. If the government of many countries are fully in support of it and have in some way promoted the use of bitcoins, bitcoins will be more in use for payments that it is used currently.
And it should go without saying that transactions would need to cost far less than today's transactions in order to replace the status-quo: people don't make a major change to their long-held behavior unless there is a significant incentive to do so.
The hardest set of people to convince to change their long-held behavior are the old and advanced. They will not really see any reason to change unless the system they are used to fails them or the new one like bitcoin offers a better incentive like you have said.