the reason might be that the young generation  have more knowledge about digital environment , digital currencies and understand the functioning of blockchain based crypto , they are more openminded and willing to change ,
plus investing in bitcoins are less hectic and comparatively easier to invest in as compared to stocks or other investments which require regulatory procedures .

now in most of the countries people  below age 18 cannot have  a bank account but if they want to start trading they can  just borrow some from parents and invest in any crypto without and hassle .