Question: when the issuance of a license costs many hundred €'s/£'s/¥'s, why don't most of these pilot's licenses have any advanced anti-fraud characteristics like for example a photo (duh!) and a much harder to fake hologram etc?
Not necessary. At least in the U.S., you can check whether or not a person has a pilot's license (and the exact type held, with restrictions and current medical) in a few seconds on the Web, because that data is public information. In fact, the whole idea of making the information publicly available in a database is to avoid this type of scenario. Licenses cannot be forged because anyone can see if the license matches the FAA database in a few seconds.
Of course, this assumes that an employer actually takes the time to look the data up, instead of just glancing at what looks like a license and accepting it at face value.
It's different with something like a banknote, which you have to evaluate on its own merits. But with a license, assuming you have positive identification of the individual to which it refers, and with access to an online database, you can see if the license is real in a few seconds. The license could be scrawled on tissue paper and it would still be just as secure, as long as you have the person's ID and the database. But you do have to take the time to actually check that database.