A computer system starts running slower and start-up time takes longer over time as user downloads and installs new programs on the system over extended period of time. Even though all of those programs are valid, they might cause start-up program list grow unnecessarily with non critical applications.

Operating systems like Windows do not have notion of delayed processing of start-up programs. Therefore when user reboots and logs on, all those programs need to run first before user can get fair share of CPU to run their own programs.