Ah, I'm not at all familiar with Eastern Europe (never got around to visit any of those countries, though Estonia specifically is on my list).

Could it be that there is less of a tradition of people walking around everywhere on the street due to the cold over there so there's no real point in having small shops everywhere or maybe something to do with the building culture from back in the Communist times (I'm thinking they weren't exactly keen on there being small businesses everywhere)?

Around here (Portugal) even with the local love for cars (not exactly the greatest characteristic of this country) people do tend to walk around in cities, especially city centers, and most housing are appartment buildings, so it's absolutelly normal for those buildings to be made with shop spaces on the ground floor.

I've seen the same not just in next door Spain and further out in France, but also in places I lived in such as The Netherlands, Germany and England.

Granted, I generally lived in or visited cities, where all the more central places (what the brits call "the high street") tend to be built like that, but for example peripheral neighbourhoods tend to have far fewer or no shops on the ground floor of buildings (and that's also the case in Portugal), though by central I don't mean specifically city centers, just areas in cities with more foot traffic (for example London has hundreds of maybe thousands of streets and stretches of street they would the call the "high street" which are really just the ones with more traffic and were in practice every single appartment building has shops on the ground floor, but London also has whole neighbourhoods with just one shop here or there)