An organization can have a content management system for their website, but that doesn’t mean they are going to use it for every update. There’s a host of reasons for that: the complexity of the update; the comfort zone of the client; the time available for the client to get the site updated just the way they want it; the client needs a customized graphic; and probably hundreds of more reasons. But update requests still happen quite a bit.
And that means that web developers still provide content updates for web site clients. Not all web clients. Not all web developers. But it’s still a relatively common practice, although not nearly as common as 10 years ago.
Most client content updates can – and should – be provided in the same day, if the client wants them online as quick as possible. Sometimes there are design/database/application issues that impact the site as a whole and it may take a bit more time, and sometimes updates come in at 11 PM on Sunday evening, but for the most part, same day, or the next day at the latest is a reasonable expectation.
A web site customer should know what standard to expect for turnaround, and get a communication from their developer if that standard isn’t going to be met. If you don’t have an expectation, ask your developer.