Depends on the car lol... After working on my brother's 2005 VW Passat TDI (diesel) I'm not afraid of having to remove 3+ parts just to get to the one needing fixed. Changing the timing belt on that car requires detaching and sliding the entire front bumper/grille assembly 6" forward just so there's enough space to get to the crank pulley and such (and moving the front end requires disconnecting the radiator, turbo/intercooler hoses and a bunch of other BS).
I don't see how removing a gas tank from a motorcycle could take more than 15 minutes, unless it's full and/or has a bunch of other stuff attached to it?