As with all operating systems the majority of the apps/programmes are not written by the platform manufacturers. Apple, Google, Microsoft et al do not produce every single programme for their operating systems, so why do users think that LG is any different? If you want a Smart TV with the largest amount of apps available then look for an Android based system.
LG's webOS is one of, if not the easiest, to produce apps for utilising HTML5 and JavaScript, the problem of lack of apps comes down to a couple of issues. The first is market share with Samsung being one of the largest in the sector, this leads to them having more resources (money) to pull in content providers to their Tizen platform, thus more earning potential for the provider. The second is that many content providers rely heavily on proprietary back-ends that do not support open standards making it harder to programme for webOS, if you reach more market share through another platform which are you going to programme for? Hotstar was one example of this with no app still available users were left to try and watch content via the webOS browser, however they were unable to do so until very recently when the site was updated to both recognise the browser ID string and serve the media in a format that could be used by said browser.
Rant over.