It seems a lot more information could be gained by fully processing a game results database then just updating a number only while looking at the previous months results. For example is a person's rating a true reflection of a wide range of players or have they mostly played in a "closed" subset of player against other players which do the same?
Additional comment question:
How do I find the results of all games that have been rated by FIDE?
FIDE publish lists of tournaments for each federation for both future tournaments that have been registered with FIDE and for past tournaments which have been played, reported to FIDE and rated. FIDE publish the data from the tournament report files here on an individual tournament basis.
That means the data is not made available to the public in an easily downloadable format. If you want the data you will have to screenscrape the thousands of web pages containing the data you want.
This also does not cover all tournaments that have ever been rated by FIDE, only those going back as far as 2001 and even then the old data recorded may only include player scores per tournament rather than individual results.
Let's look at an example to see how this works.
In December 2021 I was chief arbiter in an IM norm tournament about 15 miles from where I live. That was registered to be reported in the January 2022 list. To find that tournament go to the FIDE tournament list for England January 2022.
If you want to see other federations then at the top right hand side there is a drop down list which allows you to select other federations. At the bottom of the page there is another drop down list which allows you to select period going back as far as 2001.
Going back to the January 2022 England list you will see that all the tournaments have a blue icon on the left hand side. One of them, the IM tournament also has a brown icon. The blue icons are the tournament reports for the individual tournaments. These show the results of individual games in each round. You can see the results for the IM tournament here.
The brown icon is a pgn file link. Clicking on it allows you to either view individual games in FIDE's game viewer or download the whole file. The organiser is required to provide this file for all tournaments which have been registered for norms. Failure to do so would invalidate any norms won. Tournaments where norms are not available are not required to provide these files and so most don't.
Does FIDE publish the results of all rated games?
No. FIDE only publish all the results of FIDE rated games. They do not publish results of games played in tournaments where the games are rated by the national federation but not FIDE.
For example in the UK, where there are actually 4 federations - England, Scotland, Ireland and Wales - most chess competitions are not FIDE rated but are rated by the national federations. The same is true in the US.
In some countries, Israel for example and some of the European mainland countries, most chess is FIDE rated but there are usually some competitions for which it makes no sense to FIDE rate. Examples would be those for very weak / immature players (i.e. young children) where rules like "2 illegal moves = lost game" make no sense and themed tournaments where article 2.3 of the FIDE Laws of Chess are not obeyed.
Although Chess960 is covered in the "Guidelines 2" section of the Laws those games are also not FIDE rated.
FIDE's main rating system also only includes over-the-board FIDE tournaments. It does publish online ratings separately but only for games on its own Online Arena platform.