Rates and what you charge is a major interface with clients so it's worth taking the time to come up with a structure that suits you (first).
Doesn't work too well with maintenance on existing products; clients really would rather not pay for the hours between a PR being submitted and the PR being merged. Toss in a good dose of 'waiting for your tech lead to answer these questions', 'waiting for feedback on this proposed document', 'waiting for infra to give me access', etc, and many clients completely balk at daily rates[1].
For complete products daily billing works nicely.
[1] This is because they know that a turn-around time for granting access to their labyrinthine infra for all the machines that might be needed is going to take more than a day.
Was thinking of hitting up recruiters with my rates.
Day rate clients often don't necessarily care what you do with the time as long as your deliverables are being met – but it still helps them to pay on a time-basis as it's an easier model and more predictable