RPi is $25-35. A phone is at least $100, most probably $300-ish. What would you prefer to accidentally fry when fumbling with DIY electronics?
This one would be enough, but why stop.
A lot of space in RPi and similar boards is dedicated to I/O pins and jacks. Would you carry an 1" thick device (or even an 1.5 cm thick device) instead of your current phone?
RPi runs various flavors of Linux, RPi2 will also run Windows 10, and you can try to run an entirely different OS. Are you comfortable changing the OS of your phone? Is it easy?
Well, you see. A phone is a piece of your life-support infrastructure (think calling 911), while an RPi is an entirely different thing that most people want to keep separate.
> A phone is at least $100, most probably $300-ish.
Not really. The prices have dropped tremendously. I recently picked up the Alcatel C1 for just $9 at the local frys. Sure it is under powered compared to the flagship phones, but it is really capable enough for tinkering, it also has a touchscreen and comes installed with Andriod KitKat 4.2, which could also be rooted. [1]
The low end Lumia phones always go on sale and has amazing specs for what you pay. For example Lumia 635 (on sale $19-$49) has IPS display, 5mp camera, Quad core 1.2GHz and a good amount of sensors. [2] However the gripe with these is these are not as hackable as Andriod, so good for backup phone but not so good for DIY projects.
While you can get phones at these prices, not that they are locked to a provider and subsidized by them. The cheapest 3G+Wifi no-strings-attached phones I could find whenever I looked were always $35-$45, and it's been that way for 3 years now, and they always have mediocre specs (low res screen, low capacity battery, old android).
But they ARE usable for many uses RPi is, and they do have a working 3G and WiFi, and also a touch screen, a speaker and a battery
Verizon prepaid Moto G is $20-40 depending on the current sales. No bootloader unlock, no root, no SD slot, and no gyro but otherwise a pretty good little device for running stuff.
The Pi requires a micro SD, power supply (2a at least), USB WIFI. Once you add all those up, a cheap smart phone which includes a battery, battery charging circuitry, a camera, a touch screen and GSM seems much more attractive.
This one would be enough, but why stop.
A lot of space in RPi and similar boards is dedicated to I/O pins and jacks. Would you carry an 1" thick device (or even an 1.5 cm thick device) instead of your current phone?
RPi runs various flavors of Linux, RPi2 will also run Windows 10, and you can try to run an entirely different OS. Are you comfortable changing the OS of your phone? Is it easy?
Well, you see. A phone is a piece of your life-support infrastructure (think calling 911), while an RPi is an entirely different thing that most people want to keep separate.