We have a joint bank account where all household bills and payments get paid from.
I have set up a budget for all known outgoings (such as mortgage, utilities, food, insurance and so on), and incidentals (such as socialising, petrol, dining out, stuff relating to family stuff).
We both contributed to that pot equally when we were both working full time.
The reason we do that is that it is easier to control a set budget, and prevents overspending. If I bought an expensive gadget for example, I don't want it to cause any issues regardless of whether we can afford it or not. Besides, I feel (as does she) that personal expenses are just that, personal. I have an expensive sporty car, I can't expect her to pay for that, nor can I expect her to pay for my hobbies, and vice versa, if she wants to have a girly night out, it's for her to spend her money on what she wants.
On maternity leave, then clearly I upped my contribution and she lowered hers, it's only fair, and makes sense. And any stuff relating to family stuff is a joint expense, but stuff that is for her own is hers.
I'd behave the same way even if we both earned ridiculous salaries, because it gives us independence to spend money on what we want, and also it means we know that all the household bills are covered every month without having to think about it.
If we both contribute the budgeted amount into the joint account, it's a "fire and forget" thing - set up a standing order, and we know all our bills and so on are covered. Now, if we socialise a little more one month than the next, clearly we need to keep an eye on the money, but it's been budgeted with some contingency anyway, so if you're up one month and down the other - it all works out.
It's got nothing to do with lack of trust, or responsibility. It just makes life easier for us to know that one account is covering all our needs as a family, and our own personal accounts cover our own hobbies and lives,.