I think it's an unfair question to throw out there without conditioning the answers.
I don't believe it's possible to shower every day when you have a baby, for instance. What about single mums with no-one to babysit?
I shower about once a week at the moment, usually a Sunday. Occasionally, I'll wet wipe high-use areas in between, and can sometimes get enough time to wash my hair over the bath while DS plays in his cot.
The complications are that the shower is downstairs, so can't shower within earshot of DS - and if something is up, I can't get to him quickly.
DP gets up at 6.30am and leaves the house at 7am, I get up at 7am (ish) and it takes 40-45 minutes to get me and DS dressed and out of the house to nursery and work via a long walk and bus ride. My only option on a morning shower would be before 6.30am as DS doesn't sleep through (and invariably ends up in bed with us, so can't be left alone), so I'm knackered.
I get home at 6.30pm with DS, getting him ready for bed and asleep can take up to two hours, remaining 90 minutes of the day is spent doing bits of housework and/or spending a bit of time with DP. My only available time for a shower is in the 8.30pm to 10pm window - I can't wash my hair because I can't dry it (too late for hairdryer and no way I'd chance waking up DS), and frankly, I'm too exhausted.
So it'd be really nice if the twice-a-dayers could please not judge those who are not the same. Unless you're a twice-a-dayer with under 2s, in which case, what the hell do you do with your kids??
Pre DS I'd be a 2-3 times a weeker. Simply not possible at the moment, maybe when DS is 3ish I can start to eke out some time in the mornings?