I'm slowly moving toward not buying those things that I can use up in short order. Catsup is one of those. Everything needed is likely in the kitchen of every active cook. Especially for the simply version using tomato paste and powders. And no sugar in the make-as-needed. Mayo kind of goes without saying for any picky cook. Of course, some things are difficult or impossible. I won't be making soy sauce from scratch any time soon, and I could easily make my own liquid smoke but won't bother. But sweet chili Thai sauce is easy enough and can be modified for different emphasis for different dishes. Pad Thai sauce is easy, too, so long as you keep tamarind paste and fish sauce, but those are real basics that you need to make up many things. Pastes like anchovy and wasabi and such last next to forever in the refrigerator and take up almost no space, so I don't mind keeping them on hand any more than I mind keeping a well-stocked supply of durable spices. And having all those ingredients frees you from the choices of manufacturers of ready-mades, so you can craft something special to suit. It's just cooking.