Why is there a precision loss for floating-point numbers?
Many people can afford to buy a computer with a powerful processor and say 128GB of RAM. Maybe the same cost as a small car. 

That's enough to store one number with 300 billion digits. It's enough to store 300,000 numbers of a million digits. But it is also enough to store 16 billion double precision floating point numbers. There are problems where 300,000 numbers are nothing. 

The number of operations is another matter. That computer can probably do 50 billion floating-point operations per second. It cannot do anywhere near that number of operations with one million digit numbers. Going down from 50 billion operations to 10,000 operations with one million digit numbers, that hurts. 

Higher precision is almost never needed. And if it is not needed, it is an absolute waste of speed and memory. And remember that with a million digits precision, 0.1 + 0.2 still doesn't equal 0.3, but it equals 0.3 (one million zeroes) 4.