There are different types of collectors. For some, it is all about stamps, wine labels or coins. For others, it is about beer mats (also called coasters) - these are called tegestologists.
...beer coasters were patented in 1892 by Robert Smith of Dresden, Germany, for a very simple reason—to absorb the condensation and overflowing foam that tends to spill over the rim of a freshly poured glass of suds... Source
Initially these round or square pieces of paper were not meant to be kept due to the state of them after a few drinks. The thick paper pulp was at that time not really strong to be re-used.
However UK coasters manufacturers are now working with different materials and even the cardboard ones present in pubs can be used many times and collectors never hesitate to keep a couple for their personal collection and to exchange during some family reunions.
Technology has also improved and businesses/companies have started to get their own coasters printed with logo, slogan and branded colour. It always looks good on a desk or in a boardroom when clients are visiting.
Originally a basic item, has now become an advertising support with multiple options including shapes, colours, fonts, layout...etc - it can eventually be used as a private invite to exclusive events and then be kept as a souvenir.
Such product is not restricted to just one country but it is a worldwide item and everyone is aware of its use.
It is common to see language students bring back a few of these coasters, because it can be seen as a cheap way to keep something from a trip abroad and to remember visited places.
There is as well the fact that some people like to entertain others around a table with basic but fun games - usually about building a beermat house!
This is rather convivial and no need of smartphones or WiFi hot spot. Technology is not always necessary even if around us all the time.
Tegestologists are always on the search of the new and rare coaster either because vintage, limited edition, regarding a specific historical event or just to expand their collection.
So, if you go somewhere and see some of these, always pick one to give to an avid collector or why not start yourself a unique display which can look good framed too. Always an interesting topic to talk about when having friends and family around.