Why bed frame are necessary?

Bed frames are necessary because it provides support and stability for the mattress so you do not have a bad sleep during the night so it will not affect your health. If you do have a bed frame you should get a bed frame as soon as possible so you can get a better-quality sleep, so your mattress does not move around while you sleep. Get a sturdy bed frame to make sure that the frame does not move as well as the mattress.

Is it better to have your bed high or low? 

Having a high or low bed matters on how tall you are. A lower bed would be ideal for a shorter person as they will be able to touch the floor without their legs hanging or straining or dropping off the bed to touch the floor. The opposite is needed for having a high bed. If you are a tall person having a high bed will be ideal for a taller person. Having a high bed will give you space for storage underneath the bed. A low bed will leave no space for storage so there might not be any space for there to be dust to be underneath the bed.

Why are Japanese beds so low?

Japanese beds are low because the beds are design to be good for posture on the back, shoulders and hips so you do not ache or hurt while you sleep or when you wake up. Having the bed low will make sure that you do not fall out of the bed and hurt yourself. 

What can I use instead of a bed frame?

You can use a box spring to put your mattress on top. Other than a box spring a bed frame is the only other choice when putting your mattress onto something to let you sleep on top of it. Anything else to use as a substitute for a bed frame would hinder on your sleep quality and it may affect your health as a result.