When solving the equation $$\boxed{ {1 \over r^2}{\partial \left( r^2 E_r \right) \over \partial r}
+ {1 \over r\sin\theta}{\partial \over \partial \theta} \left(  E_\theta\sin\theta \right)
+ {1 \over r\sin\theta}{\partial E_\phi \over \partial \phi} = Const}$$ where $Const$ depends only on $r$ and $E_r$, $E_{\theta}$ and $E_{\phi}$ are three unknown functions and we assume the boundary conditions are spherical symmetric, what was the argument for $E_{\theta}$ and $E_{\phi}$ being zero?
The truth is we don't know. But when you think about it, how can we know? If we knew what technology would eventually come out of experiments like this, why would we not build that technology now?

Large expensive machines like the CERN supercollider help us to further understand the laws of nature. And through understanding these laws, new technologies arise. But we, the physicists, have absolutely no idea what wonderful technologies might result tomorrow because we invested so heavily in science today.

It's purported in 1850 after Faraday developed the electric generator, the British minister of finance asked him what practical value there was to electricity. Faraday could not have known that electricity would one day form the backbone of all modern society (but that didn't stop him from making a snarky remark). It's hard to predict the future; we labour in science in the hopes that what we do will prove useful for some new and amazing technologies. But we don't know what technologies will result from our expensive laboratories any more than Faraday knew that electricity would allow you to make a computer.
