Because in Europe no one has made money from consumer facing businesses.
European investors are all ex-banking / private equity spread sheet modelling morons who do not understand risk capital and are looking for risk free bets.
When you have this lens u eschew anything that can harm you holding onto your career. That is why.
B2B businesses have a very clear path to revenue / margin / profit.
A B2C business is effectively a punt, yes a punt, US VCs arent some sort of fucking oracles. If you look at the analysis Social Capital did for who backed the biggest co's at the series a level its effectively spread evenly so there is no "science" here.