Years ago I learned the hard way about precision problems with floats so I quit using them. However, I still run into code using floats and it make me cringe because I know som
All floating point calculations are inaccurature in a general case, floats just more so than doubles. If you want more information have a read of What Every Computer Scientist Should Know About Floating-Point Arithmetic
As for when to use floats - they are often used when precision is less important than saving memory. For example simple particle simulations in video games.