It fixed the issue on best deal runescape gold buying site. There could be some NDAs involved and there's a chance that it's similar deal as with wiki - they pay x amount of OSRS gold money for labor and resources and runelite devs then have to do xyz and keep it operating.
Since it's now there's no immediate need to switch over, but they would be quite dumb not to have some type of large scale client updates coming in the upcoming 1-5years. Everyone...