Some conversion do have a means to tie both banks together. While I can see merit in that I can also see some downside. For one, our chassis and house batteries may be of different types. I have lead acid chassis batteries while having AGM house batteries and the charging protocol is different for each.

My inverters are set up for the AGM batteries so I don't have to worry about damaging the chassis batteries or the reverse.

If I had a switch to ties both banks of batteries together, even if for a short time such as to jump start a coach with a bad chassis battery, I would want to have provisions whereby one would not pull the other down. By not joining the two sets I do not have the risk. To compensate for the absence of a means of joining the two sets I have a charger installed by Liberty to charge the chassis batteries. Not the 270 amps worth of charge the alternator can supply but a sufficient charge to restore the current in a reasonable time.