Why you can't rely on extending a USB 3.0 cable at all.
USB 3.0 + USB 2.0 Cables
There are a number of existing answers that explain how the USB 3.0 cable contains additional wires specific to USB 3.0 high-speed communication, so you can't use a USB 2.0 cable to extend a USB 3.0 connection and retain the speed.
Full-length USB 3.0 cables + hub
Jcordeiro's answer goes farther to discuss the problem he experienced trying to use a hub to significantly extend the distance using USB 3.0 cables.
Multiple USB 3.0 cables to reach 3 meters
The limitation doesn't end there. You can't even count on combining short USB 3.0 cables to reach the length limit.
As Jcordeiro's answer mentions, the USB 3.0 standard does not specify a maximum cable length, only that the cable has to meet all of the electrical specifications. The 3 meter limit is based on maximum allowable losses using 26 AWG wire for the high-speed signal wires.
The spec is concerned with cable flexibility, so it includes a range of recommended wire gauges (there are four types of wires in the cable, each with a different recommended range). For the high-speed signal wires, the recommended range is 26-34 AWG (26 being the largest diameter). The 3 meter limit is based on the largest recommended wire size. If smaller wire is used, the losses will be higher, so the maximum cable length is shorter.
So if you have several short USB 3.0 cables laying around, particularly if they're thin and flexible, chances are they were made with smaller gauge wire that is perfectly adequate for a short cable. However, they may not support being strung together to make a 3 meter cable that handles USB 3.0 speed.
The full spec is available here.