Hey, it's because they are ATPL students, so in 2 years time they willl fly big jets, without remembering what a prop or magneto is
Just kidding of course, but I also watch thes photos, any many happy before / after sightseeing flight photos with the pilots and passengers touching blades, standing right next to blades etc.
While accidents rarely happen that way, it shows disrepspect to a literally lethal part of the aircraft, which WILL develop into complacency and if the circumstances are given, WILL directly lead to a prop accident.
Although not always fatal, aircraft propellers striking humans leave scars for life: missing fingers, amputated or totally paralized arm, very badly difigured face.
And of course you won't see THAT on social media or fancy brochures.