Often, when a website is build while there is not already an older website live, it is preferred to add a maintenance page that can be published before the complete website is finished. Especially for starting companies this can be interesting, as they can already give out business cards with their website URL without people finding an empty page. When a website reaches the point that the maintenance page is live, but the website is still a work in progress, I will often already publish the website on this website.
A maintenance page can still be very flexible and can contain a lot of information that can be useful to your visitors. Links to your social media, opening times, contact information and much more is possible. Bare in mind that the more you want to customise the maintenance page, the more you delay the launch of the complete website. Often it's good to keep the maintenance page simple with just some contact information.
When you know it might take a while before the complete website is finished, it can be a good decision to make the maintenance page somewhat more developed. Besides that, the maintenance page is a page that can be used during future updates. In that case it's important to have key information and features available through the maintenance page.
In the end it's all about what you prefer. The maintenance page is useful during the building process of your website and during updates, but will take time to be customised to your liking. If requested, I will always add a basic maintenance mode to the websites I build, where you can edit the text, contact information and your logo. Possible customisations are endless, so feel free to ask me for anything specific you need on your maintenance page.