EU capital markets are underdeveloped compared to those in the US. European banks are too small, and mostly national. More importantly, the marketplaces are too small and too national. European stock exchanges are a joke compared to NASDAQ and NYSE.

There's also the small detail of pension funds generally being forbidden from investing in stocks. That's the money that's fuelling SV, if my impression is correct. This policy comes from a general risk-aversion that's also evident in all other areas.