"Frictionless" Floppies are called Hard Disks (*1), consisting of a hard media platter and a head in distance of the media (flying or otherwise)
Floppies are 2D tapes. While slower than tapes, their advantage is in (faster) random access for small data sets. The construction was made to save on tapes. They were never intended for continuous operation over long time. They are short term storage and exchange media optimized for low cost storage of small data sets for quick exchange.
Friction is reduced by picking the right materials and shape for head construction as well as low friction coatings for the disk.
Not to mention, that head friction is only a very tiny part of wear compared to the friction applied by the sleeve of a floppy (Hint: friction is applied over area - low friction over large area may give way more wear than higher friction in a small area (*2))
Also, friction is only one part of wear, as the media gets constantly warped when moved under the head.
The way to extend lifetime is to simply stop the floppy when not in use. Works quite well.
why are the drive heads apparently so close to the disk that they touch and create friction with the disk?
They are not apparently close, they touch it permanently.
A floppy is the same technology as a tape. It's in the name, they are a flexible media running along a head.
They are intended to be lower cost than hard disks (*1).
As I imagine that friction is the cause of damage to the disk resulting in a degrade of the disk over time.
That's why it's called 'Spanabhebende Datenverarbeitung' roughly 'chipping data processing' ;))
No difference to tapes. A floppy is a rotating 2D tape.
Why aren't the drive heads at least for example 2-3mm away from the disks?
Because than they wouldn't be able to detect the magnetic flux changes. IIRC the magnetic field weakens quadratic, that is, doubling of the distance results in a quarter of the field.
A floppy head gap is positioned way less than a micrometer away from the magnetic source. Turning this into millimeters means making it several thousandfold. In turn the picked up signal will be many million times fainter to make up for this the magnetization must be stronger and at the same time further apart from any change. In the end a 5.25 inch flopp may only hold a few hundred bits.
Wouldn't using stronger magnets
Stronger magnetic fields make bigger bits. Double the magnetic field means quadrupling the bit size.
Would this not drastically increase the lifespan of floppy disks as it would be frictionless?
Stronger magnets would make them useless.
Also, it still would not be friction less, as air does as well have friction. That's the reason why high end fixed disks are filled with helium - an air composition of less friction than the usual 70% nitrogen.
Now, there are floppies with 'flying' heads: Bernoulli drive.
These were floppies with a head positioned a few micrometers away. This was not done to extend life time but speed and capacity. Bernoulli drives rotated about 10 times faster(~3000 rpm) allowing density and transfer speed in regions comparable to fixed disk drives. The media was still warped, but this time upwards due the 'suction' of the Benoulli effect.
*1 - Read carefully: HARD disk, not FIXED disk. A hard disk is one where the media is not flexible. A fixed disk iswere the media is not changeable (*3). Fixed disks are usually hard disks, but hard disks are not always fixed disks. Common use of Hard Disk when talking about a Fixed Disk is simply wrong.
*2 - Yes, if a floppy is read only at a single track at all times this will be visible, but not because head wear is higher, but because the track will suffer from sleave and head wear.
*3 - Or more correct, where media and head mount are in a non seperable unit.