There are certainly good reasons for keeping your PC/Laptop clean and up-to-date. You don't want software that doesn't receive updates, or is not correctly licensed (well, you may want hooky software, but you shouldn't of course!); software which will leave your computer exposed to infection. An unlocked door is rather easy to open, after all.
A clean computer is a fast computer, and we all appreciate a bit of speed these days, probably to make up for sitting/standing in so many queues. Keeping it clean will also reduce errors which will keep you from your work, or just plain annoy you.
Everywhere you look PC Cleaning software is offered to you in web adverts. It's a big market, has a relatively low bar to entry and there are many companies trying to fleece you with fake virus popups or get rid of all your files slowing your PC down with thier "free" software. Once you have a subscription you are often going to keep it for some time, since they are easily forgotten about.
Here are some reasons why you don't need to buy into this software.
1. Windows has it all built in, for free. Windows is actually pretty darn good at keeping itself clean and tidy. Modern browsers are fast and efficient, and the cookies often necessary. Not much point in cleaning a browser for it just to go and download the page web pages content again, anyway. Opera is a good example of a browser than is clean and efficient. Chrome tends to be quite RAM hungry but is equally as quick.
A long time ago I used to use CCleaner, and at that time it was an okay tool which produced some reasonable results (in most cases). The problem has always been that Microsoft recommend you don't use registry cleaners like this, since they could well mess up your system. Would you trust a 3rd party to know all the ins and outs of every file and system in Windows? Especially a "free" tool. Windows 10 is certainly much better at managing the registry than that tool ever was. CCleaner is now avoided like the plague, whenever I see it I uninstall it right away. Not just because it's unnecessary but it was hacked a few years ago and infected a few million machines.
If you are looking to clean up your PC a good place to start is by looking for bloatware, unused or unnecessary software. Go to the Start Menu > Settings > Apps & features. Scroll down your list of applications and remove any that you no longer use. Next run Disk Clean-up - Go to Control Panel > System and Security > Administrative Tools > Disk Clean-up. Windows will check how much space can be freed up. Make sure to click on Clean up system files as that will remove updates which have been downloaded and installed, but not removed. This will give you the maximum amount of space back.
Following this, if you have a hard disk drive (HDD), you should defragment it - in Administrative Tools, select Defragment and Optimise Drives. Typically most machines don't have HDD's now, they are all SSD's which do not need to be defragmented.
2. Windows has Antivirus and Firewall all built in, it's the shield icon in your icon tray. You can double click on that icon, or search Windows for "windows security". All the icons there should be ticked green. You may find that App & Browser Control has unticked itself, don't worry this happens, just turn it back on again. This setting relates to Windows checking websites for malicious activity. Each area is customisable to some degree, so have a look through the options and research what each one does if you think you need it.
3. These apps can do more harm that good. A lot of them are just ways to deliver other apps onto your system, creating even more PUPs (Potentially Unwanted Programs). Even if they appear to have good reviews, beware.
4. They don't actually do anything. A fancy graphic may appear sporting a boost dial, and you get a fuzzy feeling of satisfaction and feel like it has done something, but it didn't. In the worst cases they will remove partial bits of the files you are trying to remove, or remove registry entries that might be needed later on (that are currently empty).
5. They could well be a scam. Organised crime is a big industry, with some of the more prolific scams making over 120,000 dollars of unsuspecting users' money.