Compare the response of local programs, such as a spreadsheet, with similar Web applications. Even if your Internet connection is 10 megabits per second, it takes time for your request to reach a server, queue up behind other users, get processed, and get a result. The server and the network itself become bottlenecks. Program size matters for a different reason than you might think. It's not a matter of download time, although that helps.
Complexity is the problem.
Small applications are easier to create, support, and maintain. Programs are disposable, because you did not spend a fortune trying to create them. Right click on the icons to see the size of the program or to view its source code. Applications are programmed in much the same way as the early web. All you need is a text editor to get started.