It’s important if your billing against a clients retainer or per an hourly contract. There’s also cases where some time might be able to count as part of the R&D tax credit.
We ask all of our employees and contractors to track time against tasks. Yes it can be a pain but it helps prevent people from spending way more time on a task than there was budget for.
A previous job made us track our hours so that we could "improve estimates," but mostly it only made people unhappy.