It’s the same for UK time trialling too. Coming from a running background I’m used to being able to plan races months in advance - and often enter next year’s race immediately after I finished this year’s. But TTs are all governed by the same body (CTT) and they seem to announce the entire calendar in one go (apparently in early december but who knows?).
To counter some of the points above about races being small, local and volunteer-lead, they still take plenty of time to organise and plan. Organisers could at least publish a date with a “pending approval” asterisk. My running club puts on two local road races, another bigger event with a national (global?) promoter, two or three smaller club/invite only races and in the past a cross country race - all of these are announced and have full details on the club’s website. Dates are published at least several months in advance for the public-entry events.
Granted the race organisation is mostly down to one or two members per event, and the website is also mostly the work of one or two people, but it can be done. Well-run committees that engage with their membership should have little difficulty in recruiting more volunteers to help with such work - we have several sub-committees that offer a less time-consuming option for those that still want to help out.