Sine Jagex is a company mostly operated in UK. The UK gambling laws are the ones that affect them the most.
Last year around this time, the UK Gambling Commission have their stance on loot box "gambling" revealed:
"According to UK Gambling Commission Executive Director Tim Miller, loot boxes in games like Star Wars Battlefront 2 and Overwatch aren’t gambling because the items obtained in these loot boxes can’t be considered money or money’s worth. What this means is that the items players get in games like Star Wars Battlefront 2 can’t be resold or used outside the game, so they don’t fall under the umbrella of gambling activity."
https://www.gamblingcommission.gov.uk/news-action-and-statistics/news/2017/Loot-boxes-within-video-games.aspx
It is really obvious, loot boxes in any game that can't be resold or used outside the game don't fall under the umbrella of gambling activity. Runescape doesn't allow players to cash out any of the in game items/currencies, TH is obviously not a gambling activity.
Apparently UK gamers learned a lot already, so no more UK Petition against loot boxes since then.