In computing, everything should ideally scale linearly or logarithmically if/where possible, except perhaps for innovation in hardware which can be nearly exponential in some terms due to multidimensionality and various other factors. Linux takes good advantage of hardware and, owing to reuse of code, programs are rarely bloated. With Windows, contrariwise, common practice/advice is to assume bloat is normal and reinstallation a routine task which mitigates bloat. Those are two separate issues; one deals with scalability and the other with the steps needed to remediate. In GNU/Linux, where malware is rare, optimising a system is often possible without radical measures like clean-installing.
It is not uncommon to see distributions of BSD or GNU/Linux running for years without a reboot or a reinstallation. These systems, which first found widespread use in (gradually more mission-critical) servers, required a high degree of tolerance, robustness, stability, and minimal downtime or rebuilding time. Windows, which had primarily emerged through the desktop, took over a decade to get the basics of networking and user privileges almost right -- an issue that still makes it attractive to rogue programs.
The three Rs, restart (application), reboot , and reinstall, have made infamous a class of box booters who are sometimes synonymous with Microsoft-certified administrators. Whereas UNIX and Linux professionals tend to deal with complicated issues of automation and troubleshooting, many of their Window-centric counterparts spend their days wrestling with issues associated with performance (setting aside restrictive licensing that impedes expansion) and malware, which are two related but separable issues. Over the years I have narrowed down the low efficiency of maintaining Windows clusters (requiring more administrators per cluster) to what some call bitrot, or the notion that digital data -- or an executable program - inevitably needs to erode over time, requiring one to revert it back to a pristine condition.
A solid GNU/Linux distribution is unlikely to slow down or break down on its own. On my main workstation (since 2008), for example, I never had to reinstall an operating system unless I switched between distributions (Mandriva was losing its corporate backing at the time). I could use the system for months at a time without any reboot. I could install over a thousand packages without it resulting in slowdown or performance degradation of any kind. It is harder to achieve the same thing with Windows, based on people to whom I speak. The three Rs are essential there.
More and more enterprises pursue GNU/Linux and people who know how to maintain it. For continuity of service and for minimal intervention it takes a system that will not 'rot' over time or be made deprecated because the company which has exclusive rights to the source code decides so.
-- Dr. Roy Schestowitz