Street protests are a wasteful activity: people walk on the streets for hours, wasting their own time, as well as the time of cops and drivers. They do this in order to have the government change its policy, but the government cannot know for sure whether the protesters represent a majority or just a loud minority, so even a well-intending government cannot really accept the protesters' requests.
A much more efficient method to achieve the same goal is a referendum: instead of hours on the street, you spend just several minutes in the polling booth; then the outcomes are clear and accurate, and if your opinion wins a majority, the government is obliged to accept it.
Therefore I would expect that a country with more referndums will have fewer street protests, as people who can affect the policy through a referendum will have much less incentives to waste their time on the streets. An extreme example of such a country is Switzerland, in which every 100,000 citizens can force a referendum on any topic. This gives rise to the empirical question in the title:
Are there fewer street protests in Switzerland than in other democratic countries?