As with most things in life, you get what you pay for.
In order for a stake pool to be continuously updated, monitored and cared for, you need professional management and a complex setup. It’s not free to run the processing power behind the nodes, nor is it free/easy to provide all of the management and updates needed to keep a stake pool up and running 24/7.
Pools with 0% fees are not incentivized to perform their best. In a 0% pool, the SPO only makes money from the first block each epoch, as determined by the pool’s Fixed Cost (generally 340 ADA). The income from a 0% pool would not be enough to cover the server fees alone on a monthly basis, nor would it be able to pay the operator for her time.
We recommend choosing a pool with a 2-4% fee to help ensure the pool is at its max performance and has a SPO dedicated to the project.