In case of real estate, depreciation offers income tax deferral because real estate retains much of its value and sometimes even appreciates despite being fully depreciated. It may be a part of or analogous to the borrow and die scheme of tax avoidance.
To others, it's a source of pride. They love driving a car that still look factory new despite being 15+ years old.
And others, it's a source of fun.
I'm in both of the latter two. I drive a performance EV because it's fun, and I really like it being clean and shiny. I got it wrapped in paint protection film, then covered in ceramic, to help keep it looking its best.
Will it help it maintain value? Not really. Certainly won't get any of the $6,000 I spend on the PPF and ceramic back. But I don't care. Not everything you buy needs to be considered an "asset" that you worry about losing value on. It's okay to buy things purely because you enjoy them.
I don't see a correlatiopn between depreciation and the cleaning of the asset. My body for example started to depreciate after it was appr. 30 years old, but I still wash it every day. I think cleaning is an operational expense that does not support the lifespan of the object, it merely maintains an experience threshold.
And about experience, I also never washed my car until I got kids: car washes are an experience in its own right nowadays.