You're right, it does happen, but not frequently respectively on a large scale.
For example:
1- it does happen that sometimes some illegal trash bags are found in the woods (most of the time it's still in trash bags and not spread everywhere as they usually don't contain animal/vegetable stuff, as that would anyway be free to be disposed of, therefore animals don't sniff it therefore they don't mess it up), but then they're reported to the police/municipality by whoever discovered them and are then collected.
2- same thing in urban areas: sometimes (very rarely as much as I know and have experienced) some "illegal" trash bags show up in your own trash-container, then usually you have to talk to the trash collector and they'll still pick it up.
But:
- about case #2, as mentioned in Wikipedia, the analysis of what's contained in the illegal trash does happen for real (kind of "CSI: Trash"), so if I would put into it something which shows my name (e.g. old newspaper) then I would be screwed (probably not the first time, but I would be by the 2nd or 3rd time that the same thing happens). Even if I would do everything perfectly then after at least the 2nd time all neighbours would all try to find the perpetrator => high risk.
- about case #1 and in general, the country is small and has a relatively high density in the habitable areas (e.g. not in the mountains) => many eyes around, so if you keep doing that twice or three times you are likely to be noticed by somebody, who will report that to the police or at least the municipality - same thing about rural areas (fewer eyes but as well fewer visitors, therefore likeliness of being observed doing something bad after repeated offense is still high). Nothing in the mountains as far a I know (too much effort driving up there to then take the risk to dump stuff while potentially being photographed from the other side of the valley by e.g. someone that was doing trekking).
I believe that we don't have problems with electronics like TVs, washing machines, HDDs, fridges, etc... because you can just dump them for free at any shop that sells them (that's the embedded-tax-thing I mentioned above), so it would be a waste of time & effort plus a lot of risk to dump them into the woods instead of doing the same thing comfortably and officially at any such shop (I admit that some shops get more old stuff than others due to their location and parking space, but nothing is perfect).
In bigger countries that have more open/free space, illegal dumping would most probably be a much bigger problem. But on one hand people that do repeated illegal dumping could still be caught, and on the other hand the target is never 100% - already having something like 75% of the population sticking to the waste disposal rules (recycling being a subset) is probably a huge improvement vs. doing nothing :)