It starts out early in life when we break something but hold onto it because we might be able to fix it someday or we might be able to use some of the parts to fix something else. The reality is that we very likely will never use nor need that item again - assuming we could even find it when we wanted to. It sits on a shelf, gets tucked away in a box, or sits out in the basement, garage, attic, or closet.
We have tee-shirts, pennants, posters, or other mementos or souvenirs from concerts or events that we attended years ago. How many tee-shirts - possibly faded, stained, or too large or too small to wear comfortably now - do we really need? Do we really want to wear something that obviously is from many years ago with the date of the game or concert on it?
We have expensive clothes or shoes (at least for the time when we bought them) that are no longer in style, don't fit us anymore (because we weigh more or less than we did at the time when those items were purchased), or our tastes in colors or styles have changed, but we store them in a truck, closet, or storage facility because we just can't justify parting with them, think that they they might come back into style, or feel that we might be able to wear them again someday.
How about tennis rackets, racquetball equipment, hockey gear, bicycles, baseball outfits and equipment, skates, bowling balls and shoes, and other sporting goods or recreational items that we stopped using long ago but hold onto in case we get an urge to pick them up again and start using them? We paid a lot for them at the time we got them and we feel that they are just too good to get rid of - despite the fact that equipment keeps getting better, stronger, lighter, streamlined, and efficient with technical advances over the years. Our old gear would probably look out-of-place or be noncompetitive even if we did decide to use any of it again. Some of it may have even deteriorated from lack of use over time also.
Take a small appliance like electric cookware, coffee maker, deep fryer, blender, mixer, or similar item that becomes broken, burns out a heating element, has a timer or thermostat go out, doesn't perform as it once did, or otherwise is not the same as when it was new, but we hold onto it because we may get around to fixing it someday, it was such a good appliance, or we might be able to use part of it to replace something on a similar item that we put in service after we retired that item.
Sometimes we buy several items when they are on sale because it is just too good of a price to pass up, but then our tastes change, styles change, the items go out-of-date, or we find that we really didn't use as much as we thought we would. So, rather than toss out the surplus, we hang onto it - just in case.
We don't start out to clutter our lives and our homes, garages, basements, attics, closets, and sheds with a collection of items that may lose their value to us over time, that may not work, that are missing an important part or element, that are of a color or style that likely will never return to prominence, or that we couldn't find even when we wanted to use them. We just hang onto one thing here, and one thing there. After a while, we have retained a lot - not just us but so many others also.