I think it's a mix of several things:

- A bloated public sector that is protective of it's jobs and represents a large percentage of the electorate (also very motivated to go on a massive strike if you even think about reducing the complexity of the system)

- An aversion towards real capitalism. Europe is still pretty much a class system. It's ok to want to have a better education and job than your parents, but wanting to do something more spectacular is almost equated with "being up to no good"

- You cannot be fired from a public sector job, so you have absolutely no incentive to care (some people still do, but they're not the norm)

It's just a way of identifying that a document is 'officially' from the company.

Ideally you just lock up the stamp in a drawer. You can probably forge it just as easily as others, but at least with the stamp multiple people can "sign" for the company. In my experience it was more useful than anything.

also: it's not euro-only. Go to Japan for a laugh if you want.

China also.

And then there is also the fapiao (stamped receipt).

Getting the stamp on the 20 euro electronics purchase is in the customer's best interest as it is a proof that he purchased the item there and so can get warranty service from the seller (I don't know if "warranty" is the correct term here, in German we have two words for two concepts that wikipedia both links to the English "warranty" and that most people confuse anyway: "Garantie" (cognate to "warranty") which is a voluntary service offered by the producer, and "Gewährleistung", which is a legally mandated service by the seller. The stamp documents your right to get "Gewährleistung" from the seller who puts his stamp on your receipt, and usually the producer's "Garantie" requires that stamp, too).

It is more difficult to forge a stamped receipt, true. As to whether it proves that you purchased the item is debatable because both a receipt and a stamped receipt can be easily forged. The question is: is it necessary? Tally up all the man-hours a country spends stamping receipts. Could that time be put to better use? North America seems to function fine without them. Perhaps we've come to realize them as redundant - or are we too gullible to not demand rubber stamped receipts in the first place?