I know why Forge does it to get money for the effort they put in, but its getting annoying so I just use Third Party Launchers instead to skip the Forge 'ad site' parts and the rest of the mod downloading I do safely. With the Third Party Launcher Forge is easy to download once you select the Forge you want and it just gets it with ease, no problems like ad site nonsense to deal with like the Vanilla Launcher.