Dispensers are the answer. Leaving out a partially-used bottle of supermarket-bought shampoo just seems a little off. God forbid a used bar of soap! My hand soap is in a hand soap dispenser next to the sink. For the shower, I bought a shampoo/conditioner/body wash dispenser, which is nice-looking, affixed to the shower wall and doesn’t reveal the fill level of the products. This way I can buy big bulk-size tubs of relatively cheap brands and just fill the dispensers. I’ve gotten several compliments from guests on the shower dispenser, saying they feel more comfortable with that, rather than with half-empty store bottles of Suave with some well-used soapy scum on the bottle, which they’ve seen elsewhere.
For the kitchen, I have a hand soap dispenser built into the sink. For dish soap, I’m fine with having a bottle available, which people continue to use even if the bottle is half-empty. I figure that’s a less-personal product, as compared to something you slather your body with. I also provide some canola oil, which I provide in a squeezey bottle.
Incidentally, I also have a small pack under the bathroom sink with a couple of individually wrapped cheap razors and a few feminine items. They rarely get used but people appreciate them being available in a pinch.