Why do PCs get slower when nothing changes?

[LeeUK]

How come you buy/build a PC with all the current hardware and it speeds along happily. Six years down the line it ends up all bloated and sluggish when nothing has changed, same software, same web browser, nothing else. CCleaner, etc, ran regularly but just goes slow again after a day.

Is it some conspiracy theory to make you get a new machine with the current up to date tech, just for the same thing to happen again a few years down the line...?

 

[LeeUK]

Same with phones as well. When I first buy one, I download all the apps I'll ever use and that is it. Nothing else gets put on there, pics are saved to cloud, etc. All is fast and snappy, but then a year down the line I end up wanting to throw it at a wall because it's gone so frustratingly slow and laggy.

This is the same with my iPhone 4 I've had since 2011.

 

[LeeUK]

I defragged not long ago and when I did it wasn't even fragmented much. The only AV and firewall I got running is that Microsoft standard install one.

Ran CCleaner last night and PC is already bogging down again tonight.

 

[LeeUK]

I only run updates manually, never let them do their thing in the background. CCleaner makes a difference when it has cleaned 500MB+ of history away but don't notice again after a few hours.

Thinking about getting an SSD then install a new current image of Win7.