"Website as a service" sounds like marketing language, so it is worth being plain about what the monthly fee is actually paying for. Underneath it, a live website is not one thing. It is about six things that all have to keep working at once, and every one of them can quietly stop.
Hosting
The computer your website lives on, running all day, every day. If it stops, your site is gone until somebody notices and restarts it. Hosting is billed monthly or yearly by whoever provides it, and it is the single most common reason a site suddenly disappears — the card on file expired.
The domain
The address people type. You rent it, usually a year at a time, from a registrar. Miss the renewal and it can be bought by someone else, sometimes within days. Inside a plan, this renews automatically and you never see the reminder email you would otherwise have ignored.
You still own the domain. That is not something a service should ever take from you — if you leave, it transfers to you.
The SSL certificate
The padlock in the address bar. Certificates expire, often every ninety days, and when one lapses browsers put a full page warning in front of your site telling visitors it is not safe. Renewal is automatic when someone has set it up properly and catastrophic when nobody has.
Backups
A full copy of the site, taken every day and kept for a month. You will almost certainly never need one. The month you do — a bad update, a wrong deletion, someone getting in — it is the difference between an hour of annoyance and rebuilding from nothing.
Edits
This is the part people underestimate. Prices change, staff change, opening hours change at holidays, photos get out of date, a paragraph reads badly once you have seen it live for a week. On a one-off project, each of those is an email to a developer who may or may not still be free, and an invoice. On a plan, you send them and they get done.
The reasonable boundary: an edit changes something that already exists. Building a whole new section, or turning a business site into a store, is a different conversation — but it happens inside the plan rather than as a new project.
Updates and fixes
The software underneath a website changes constantly, and out-of-date software is how most small sites get broken into. Keeping it current is dull, endless, and the reason the plan exists.
Speed and uptime
Somebody should be watching whether the site is up and how fast it loads, and it should not be you. A site that takes six seconds to appear on a phone loses most of the people who tried.
The short version: a website is not a thing you buy once. It is a thing that has to be kept alive. The monthly fee is what keeping it alive costs, with the building included.