Who should the people responsible be for Lightning's business development?
No one, after all Bitcoin community (and some open source) is powered by volunteer.
or "everyone"
those who refuse to provide incoming liquidity to others are not helping the network (including those who charge a fee to do so, but that's my opinion and their prerogative)
we can all help the situation by identifying nodes with low or no incoming liquidity, and providing it to them by opening a channel. I realize that there's potentially more fees to be earned opening channels to nodes with higher routing throughput, but ultimately, a better connected network is stronger (and more profitable in all aspects) than a centralized network. There will doubtless be a limit to how may channels it's useful for a single routing node to have, although I am unsure what that limit is (it's likely related to the amount of traffic on the network considered over a long timeframe, as well as how much BTC a node has to put into the network).
Altruism. But reality is, without incentives, Bitcoiner's can't be expected to take/accept the opportunity cost to lock their capital, Bitcoins, in Lightning channels.
Leading on from that topic, does electrum lightning allow capacity to be added (it'd not just lnd) I found a wire in the back of my router I was going to use to put a node on a pi, I could instead open 30 channels with 0.003 btc on each capacity wise to help fund the network a bit more and I think it's a pretty cheap way to do it as well... (this is all dependent on whether I remembered to bring a hdmi cable with me as lockdown will make it impossible for me to source one I think).