It's not necessary to use the household bin on the NRaas SP source of genetics options, that's only one of the three different possible sources for sims' genetics that are applied as they spawn. Some players really like the seed the bin feature, others like me can't stand using it and keep it switched off. Although I've had some funny rapid immigration accidents happen with bin stored households being used too much over the years when I forgot to set things the way I thought I already had.
The other two sources are:
-- Random Sim Generation. This is EA's way and does tend to lead to zero-slider sims. It can also be switched off, but I keep it at around 10 or 15% because in real life some people are indeed "plain" looking.
-- Existing Sims in the World Get Used (to create temporary parents/genetic donors who are then discarded behind the scenes). If your world is already full of diverse looking sims, this option will give you more and with blending taking place. If it is already full of zero-slider sims, you will get more of those. This is the option I tend to favor.