It’s easy to take a worn part out. Not as easy to put a fresh part in.
You know how, when you put on your old pair of shoes, your foot just slides right into them, but then you get a new pair and you may have to use a shoe horn, or maybe a couple of fingers behind the heel to get your foot in?
Well, the same thing happens with car parts. That old fan belt came right off, but the new one takes a little bit of effort to get on.
Those old springs fell right out, but the new ones takes a little bit of tweaking to get them in place. After all, there’s a reason why hammers come in different sizes, and pry bars come in different lengths.