Lifestyle - that's my belief. Some people are naturally very clean.
I have been cleaning houses for a very long time, and some feel incredibly clean when I arrive...it's only when you get down to it that you can find the dirt. Other houses look and feel no better even after a good clean.
The houses which look and feel clean are the ones where the owners have a rational handle on cleanliness, and make sure kitchen & bathroom surfaces are attended to after use, things are put away, clothes are washed properly & laundry is up to date, beds are changed, and they use lots of coasters & things under things, as well as door matting, to reduce the dirt and associate smells to begin with.
Bad smells are also a sure-fire way for even the cleanest home to feel utterly rank...bathrooms can smell really damp in a special sort of damp-mixed-with-dust-mixed-with-pee-with-no-fresh-air, especially if they have carpets. But simply having scents around the house rather than having fresh air and laundering furniture covers, bed linen, coats etc. will only put a layer on it...smells need to be found and irradicated, not covered up.
Regarding the floor grout looking off, it could be that as long as the tiles are clean, along with the other parts of the room, it may not look that bad...sometimes seeing that one thing isn't clean in a room that clearly is clean can lessen the impact significantly. This said, it never ceases to amaze me how people frequently choose floor and wall coverings which look dirty to begin with...and far from the pattern hiding the dirt being an advantage, it has the disadvantage of never knowing if or even when the floor is actually clean.
I know I'm biased about grey carpets as I don't like the trend for grey at all, but grey carpets to my eyes never look clean, simply because grey is the colour many a carpet goes when it's grubby.
Perception plays a huge part in the psychology of "clean", but without looking around your home, I couldn't say what (if anything) you could do differently.