socat is a "dumb" tool. With a proxy that understands HTTP you have a lot more influence over what goes where and for example not direct requests to a down backend instance.
Are you challenging me to build a socat loadbalancer in bash? In all seriousness, I concur. But if you just need to redirect some data streams socat is a rock solid and simple solution.
From a quick read of the manpage, I don't think it's possible either, unless you mess with EXEC or create multiple listeners to a single address.
Anyway, the Linux kernel does have a builtin loadbalancer in the form of shared sockets that you can socat outside of the machine. But I wouldn't call that a socat loadbalancer.
