We will never manage to get a decent salary for (less than very senior) instructors as long as so many fully qualified pilots are prepared to fly for free, or even PAY to fly, just to build hours.
How can you expect any commercial operation (flying school) to turn away qualified staff that will give them money, or fly for free?
Of course it's a combination of eager enthusiasm and clear lack of industry education that has these folks begging to be allowed to work AT ALL - but as long as they are willing and able, it's game over for the reputable instructor with a bit of experience.