You are absolutely right! Corporations and small businesses try to wring the last molecule of depreciation out of their computer systems before upgrading. As the result, many firms, large and small, lack the latest free built-in security for their computer operating systems.
Obviously, many home users cannot buy a new system every year. They can, however, allow Windows to perform automatic upgrades. They can install 3rd-party products, such as CCleaner, Super-Antispyware, Malwarebytes Antimalware, and Spybot Search & Destroy, all of which offer FREE versions for home use. When you try to open a sketchy website offering PR0N or free stuff, or Email from people you don't know, these FREE products will either block your attempt or else give you an on-screen warning.
Last, but not least, install and use an Anti-Virus product, which is not the same as anti malware products. Windows Defender comes with the Windows OS. There are free versions of most popular Anti-Virus products, such as Avast, Avira, or AVG.