LoL has specific forum rules for that section limiting it to the Donor Forum.
LoL RP trading carries a fairly high risk as opposed to other games, where both parties would get punished harshly in the event of a scam, with the person purchasing being at the greatest risk.
If the person selling the RP charges back the funds, then both the account they sent the gift with and your account will be locked pending repayment, along with a black mark on your account that increases your risk for punishment.
If this happens several times, your account may be permanently banned. This may not be a concern to the seller, as accounts are free to make, and alt accounts to sell RP would be easily recyclable.
People pay for a chance to get into the Donor Forum, and are often less likely to screw you over in a high risk trade such as this.
To add to that, LoL has a stricter gifting policy that doesn't allow for immediate gifting to take place, and thus would delay any trades.
And the only form of immediate RP trade would be through a RP card gift code, and trading of codes generally isn't approved in any subforum here that I know of.
If LoL were a safer environment to trade in, people would most certainly be doing so.
BDO doesn't have these specific forum rules, and this form of trade does not go against the general trade rules.
If you need another example of things that you can spend $$$ on and sell for forum gold outside of the Donor Forum, you could refer to the Steam and CS:GO subforums for great examples.
This post was edited by Kokua on Jun 14 2018 12:18pm