The bar of entry is much higher and Smart Phones are designed that way. It is impossible to play around with programming on Smart Phones when you need to either Jail Break the phone or pay for expensive licenses.

The last thing companies want to happen with smart phones is what happened to PCs. People were able to upend many large commercial companies in the 80s and 90s due to the low bar of entry.

Just to name a few: DEC, CDC, Data General, Wang. IBM almost folded due to the PC. So Smart Phones were made closed to prevent the same revolution from repeating itself.