Actually, a booster
can increase speed. The prerequisite for this to happen is that there is more bandwidth available to the wireless access point than it can serve over a low-strength WiFi connection. This is not usually the case in your campground, but will be when you are connected to a less busy access point. WiFi comes in a number of different modulations and bandwidths, and switches from one to another depending on the signal strength. The highest bandwidth connections require a strong signal. When the signal is poor, WiFi will go down to less than 1 megabit per second, and the maximum performance possible is over a gigabit per second.
The speed can further degrade because every transmission must be perfect or it must be repeated. So, if two stations try to send a packet at the same time or if there's noise, packets will be dropped and will have to be retransmitted.
We also have complications like the Hidden Transmitter Problem. A booster can help with that.
shows some of the different modulations.