Yeah people are notoriously bad at noticing odours they are acclimatized to (anyone who's given up smoking, been to a convention, or talked to someone living in a smelly area can attest to that).

That's not to say they couldn't smell fine without daily showers but a smell will certainly build up over time. Some might be lucky and it won't smell particularly objectionable but you will smell and will smell stronger over time.

They need to check with someone they don't live with(so they're not used to it) and that someone will need to be willing to be blunt with them.