I too use DHCP with reserved static addresses assigned. I find this to the be best of both worlds. My individual devices are set up for DHCP, so if there was ever a networking issue, or I had a need to bench test a device or other similar situations, I would be able to connect to the device without any problems even if the "local network" I used for that purpose was different than my regular network scheme. However the router will assign the same reserved IP address anytime that device comes onto the normal network. This gives me the consistency of a static IP address so that managing those devices is easier (via network GUIs) as well as insuring that my camera feeds in BI and other home automation functions/systems still work reliably even if the network gets reset (power outage, router software update, etc).
You obviously don't need to reserve addresses for every device however. There are plenty of devices (like mobile devices) that only need to be on the network but don't need to be accessed by other devices on the network and therefore don't need a reserved address. Furthermore, mobile devices likely to be replaced more frequently than any other devices, so there is no need to add "extra work" by assigning reserved addresses for them. Even still, I have over 100 reserved addresses assigned in my pfSense software spread out across multiple VLANs.