It may be beneficial for you to go actually read all the documentation for PortabilizeMii and The Definitive Wii Trimming guide.
PM was designed so that you can trim the Wii to roughly the size of a credit card (OMGWTF trim) or smaller (LMAO and OMEGA trims). It installs Custom IOS' that allow us to remove the Wifi, Bluetooth and Disc Drive from the Wii and still have it boot. The NoWifi IOS' are those custom pieces of software. PM also installs PostLoader, a customizable front-end for loading games and playing emulators.
Some users want to have PM but still have Wifi, so we made that selection an option.
Wifi isn't really that beneficial to a portable (IMO) Yes, you can stream Netflix and I believe there are some online servers for games ( Project M, iirc) and you can download homebrew but after trimming, it's a big pain to relocate the wifi module.
It's up to you, but that's why it's included as an option in the PM generator.