SMC and NVRAM resets: why not just do them by default?

You really should not need to perform these resets very often.

Sometimes the NVRAM will become corrupt necessitating the need to clear it by performing a PRAM reset. If you reset the PRAM, then you are wiping out some settings such as the "Startup Disk" so when you reboot the computer it will take longer to boot the computer since the computer must now search for all available boot volumes (internal drives, external drives, and even network volumes) before deciding which volume it will boot from. Resetting the PRAM also resets the Date & Time preference. A PRAM reset also resets your volume & brightness settings to defaults.

An SMC reset usually only needs to be performed if the computer has encountered a power issue which may have corrupted the chip which manages the power. Usually this is caused by a power issue in the home (or power outage) or by letting a laptop's battery drain to 0% for an extended period of time.

If you need to perform either one of these resets more than once in a long while, then you should look to see what is causing your computer to need the reset.