It's so that in the event of mechanical failure a pilot can always rely on a magnetic compass for navigation, without having to know or look up the magnetic variation of the airport.
Also so there’s no confusion, each direction is named, so a runway that runs due North-South will be Runway 36 in the northern direction, and 18 to the south.
In practice it is rare for all but the largest airports to have more than 3 or 4 runways so it isn’t like there will be a Runway 2 and a Runway 3 at the same airport. If they need more capacity they’ll build parallel runways which will be named with a suffix, like 9L and 9R.
(Also, magnetic compasses aren’t that accurate in the first place, since there’s iron in the engines if nothing else. In theory there should be a compensation/calibration done with the results on a card, but, no guarantees that it’s done or up to date).
There are even some airports that have three runways with the same heading, so they have "L", "C", and "R". (Two examples that I've personally took off or landed on all three of are 17/35 at DFW and 01/19 at IAD.)
There would be no (or extremely rare, at a minimum) operational reason to alternate directions for takeoff and landings on parallel runways. (There are rules for simultaneous operations to parallel runways and having them be in opposite directions would be problematic as you have to assume some aircraft will execute a missed approach and would then be climbing into opposite direction landing traffic with only a small lateral offset.)
In fact, taking this dodge into account, the DFW example I gave actually has five parallel runways; the two they label 18/36 are actually the same heading as the three they label 17/35. I wonder if they'll ever need to go to six and add an 18/36C.
Doing that for 4 would need one direction to be A B C D and the other to be B C D E (which is workable, but doesn't seem particularly more elegant than just using left, right, and center [and in fact is worse in some ways, since from one direction, B is the left-most and from the other, it's A])
Then you have airports like ORD which have more than three parallel runways - but pretend some of them are ten degrees off to get more naming space. [1]
[1] https://upload.wikimedia.org/wikipedia/commons/a/aa/FAA_O%27...
My flight instructor once switched off the electricity to the airplane's controls and radios and told me to land. At an airport with a control tower. Using the magnetic compass, airspeed, barometric altimeter, RPMs, that's it. Nothing else works without electric power. There's a whole procedure for doing all that. Being able to navigate safely with an old-school magnetic compass is life-critical.
You just pre-arrange it with the tower and it's no big deal. Probably exceptions for busy class Cs or Ds, but it's no big deal to any airport near me.
Also, in the real world, i would probably break out my smartphone. Short of an emp strike, it will still run on its own battery and can act either as a rough set of instruments or to phone the tower and declare an emergency.