Floppy disc or magnetic disc are faster and mor flexible than tapes. you can load and store autonom (no start and stop) and not linear, you can store them here or there. but of course also expensiver (you cant anymore use a (music) tapedrive.

Tapes comes from the mainframe tapes and were popularised by music too. so often people used normal tapes-drives and for a zx81-games - there were even description how you had to connect the microphone-cable to the head-phone-jack and reverse. While loadibg a zx-81 game you hear the whole time the data coming in! so meta: sound was for people and maschines.analog digital. So there was no difference between an accoustic coppler and data from the tape. 

The bootsector allowed an automatic startup (vs tapes) of games like in consoles with cartridges (of course a lot of games came also out as cartridge for computers). Put it in and switch on computer and play. Of course the bootsectorviruses were a sideeffect of this innovation. 

sending information via snail mail on disks

most possible reason: you could several discs put into a letter. 

come in with your original. come back in one hour. you get the original and  the cracked game back on floppy disc.

War Heli is a state of the art shoot em up game with big sprites on a computer with no hardware-scrolling! 

Make games copyable. Some cracker groups where in the tradition of information freedom, others learned from cracking software creating software, others had fun, others were in a sport ‘who is first’ and of course also others gained money. 

Why switzerland? and not us? The rumor is: There was no law in switzerland against cracking. 

With modems1987  and zterm you could enter to a bbs and download software. You needed the number and of course a computer on the other side. So this bullet boards system where dial in systems. from time to time the mother of a guy took the phone .-) 

You only used this in the ‘phone cheap time’ - >21.00. A game for Amiga or Atari ST was 900kb - the modem was about 3600-12200 bauds. you waited very long from time to time.

Software tries to read something from the disc. Could not read it. You can try it several times. Handling errors. It is no 1 or 0 it is an exception.

A copy makes a 0 out of the whole. And the software can detect this - it is nether 0 or 1. 
 

Often used - enter data from cover or description. 
With more and more photocopiers, often used bad copyable sujets (red etc) or complex systems like rotating discs (several lucas arts games  and were in the mood of the game).

Later the dialog to enter the number/code came in the middle of the game (manic mansion etc). 

Codes were also used to ‘store’ progression.