There are many factors affecting the adhesion of FDM prints to a print bed, be it incorrect print settings, dodgy filament, or warping due to temperature effects. And this can become more of a problem when using filaments more advanced than your typical PLA.
Take PEEK or ULTEM for example. These materials require incredibly hot build chambers to print parts correctly, without warping. And even then, adhesion can still be an issue, especially if the chamber conditions are sub-optimal.