It would not be popular mostly; these are departmental apps in big corps built on top of subsets of the 1000s of tables. They can contain some business logic, but that can be ‘no code’ as well (flow chart kind of stuff); these systems are usually not the nicest to use, however much (!) nicer than the systems the tables originally belong to. So see it as a small team/person needs to enter certain type of data; they can learn to wade through miles of SAP menus, or someone clicks together a little crud (web) app that does exactly that and cannot do anything else. There are many 1000s of these cases, but they do not get popular as they stay inside the companies (departments) they are created in.
The big spreadsheets that everybody in a department use always evolve into a mess full of VBA.
I am yet to meet the mythical CRUD app that could be created without code.
Now, if you go into "low code" as in a very high-level opinionated framework+language, that can work. But if you start from CRUD generation, you won't reach anywhere useful.
I guess the definition of code is missing; as a coder, all the graphical settings etc is also code and in that sense, there simply are no no-code solutions. But if we say configuration (with dropdowns and checkboxes and such) vs code is no-code then there are and I have seem these work in actual companies. We delivered quite a lot of these when I still did that type of thing; for instance, a lot of the internal (intranet) software for political parties and unions in my country we just generated with our own point/click code generator. It was simply crud with roles/permissions etc on top of their internal (ms-sql or access at the time) and many of these applications were used for many years internally. But I agree ; if you call a spade a spade, only 'low-code' exists and no-code shouldn't be used. That's fine.
I guess 'useful' is in really who you are asking; people working in department X in country Y of huge intl corp Z are usually not very happy what the 'headoffice' bestows upon them as software packages. Restrictive, everything has to be coordinated with those scary people from IT etc etc. To be able to change that without breaking the bank can be very empowering and has been the domain the domain of low-code (and no-code) tools forever; from Excel, MS-Access to Wordpress to less well known systems.
One of the biggest electronics retailers in the EU has a central, restrictive, very annoying massive enterprise CMS which is pushed down by the headoffice; every local country started pushing out WP sites; low code (html/css (they have to use the house-style, so they copy that from the main site), the rest is plugins and some shortcodes) needed and cheap while not having to wait for 6 weeks for permission to change 1 sentence 'by IT in the homeland'.
