I’m not sure that incentivizing by distributing fees to validators achieves anything.  Several problems with this approach, but let’s start with this: Which validator would half the fee be paid to? Even if you could, somehow, distribute half the fee among the validators (and I don’t know that you can meaningfully do that) you still have another problem:  Validators can already vote to adjust several network parameters—from the account reserve to the transaction fee. By paying validators part of the fee you change their incentive. Now it’s no longer to fairly set the fee to what is appropriate for the network, but to set ad maintain the fee at the absolute largest fee users are willing to pay before “rebelling”.
If it’s split among all, what you’re doing is incentivizing people to spin up validators that are there to collect a fee and  don’t really add value to the network.  You want validators that are invested in the long-term health and success of the network; not collecting fees. More validators are good, but what you want validators that you can trust to not collude. By incentivizing validators through fees, you give them an incentive to collude: the higher they set the fee, the more they make! So while more validators are good, what we want are validators that are not operated by rent-seekers but by those that believe that the long-term health of the XRP Ledger is important.
People don’t run validators out of the goodness of their hearts.  They do it because they derive value from the XRP Ledger and it is in their best interest for the network to be healthy and have a broad and diverse set of validators. The incentive is rational self interest.

by Nik Bougalis (https://twitter.com/nbougalis)