Why does going into an Apple store seem to make people more likely to part with significant sums of money? The same could be asked about any retail presence really.
The truth is people want to acquire things, they want to give you their money. They've been subjected since birth to the most well developed science known to Human history: How to seperate people from their money.
In retail you've got to have a hook. It can be price, service or some gimmicky bullshit that looked at objectively adds no value to the purchase, but it activates those conditioned responses.
In the case of Google products, they aren't going to be competing on price, they obviously aren't going to be riding on service, gimmicky bullshit is all they've got. Besides, it's almost certainly cheaper to buildout a barge than rent prime retail space and you've got loads more options than in a managed retail area.
As far as webinars, the bulk of consumers aren't going to explore products solely online. They've got to see one and hold it before they buy it. People more comfortable online (like you, presumably, and I) are far more likely to do some research and be comfortable making a purchase based on what we've learned. The vast majority of people aren't like that though, hence the whole 'showrooming' thing. If Google wants to get into the mass market they've got to cater to that majority.