Wifi auto rejoin issues on Nexus 5 / Android 4.4
It appears that this was an issue from Google's syncing of wifi profiles from older phones. For some reason, when my new Nexus 5 acquired the wifi profiles from my Galaxy Nexus, they exhibit this issue.

The solution here worked but you must be rooted. You must delete all the wifi profile data (requires root) and then re-join the wifi networks again.

adb shell
$ su
# rm -r /data/misc/wifi/
# reboot


Then rejoin your wifi networks in the wifi manager. When you leave the range of the wifi and come back, it should reconnect as normal.