So what do regular aircraft do when they run out of fuel? They require a forced landing. Aircraft fly with a buffer of fuel though to avoid such situations, so why can't an electric aircraft fly with a similar buffer on it's range? ie. Always fly less than the current charged range of the aircraft.

Regular aircraft are required to have enough fuel to be able to divert to the alternate airfield in their flight plan plus all the margins for taxiing and waiting for a landing clearance. If a plane is low on fuel they can declare an emergency and get priority over other traffic, but that obviously is disruptive and should not happen on well planned flights unless something pretty significant happens after takeoff.

Regular aircraft fly with enough fuel to change into at least one other airport in an emergency (ideally two).

That aircraft would need a very large battery to do that, and it's way more efficient to have some burnable fuel there that you'll never actually use.

Simply put, batteries are heavy.