Is there any reason not to have tube phono stage ?

why not tube phono stage.

@inna Here’s a reason for a tube phono section:

If we are talking about a LOMC cartridge, its inductance in parallel with the capacitance of the tone arm cable sets up an electrical resonance at Radio Frequency (RF) frequencies. For example a Lyra Titan might be at about 5MHz. 

Because of the design of the coil in such cartridges, the electrical peak is pretty sharp (in radio parlance, high ’Q’). It can go into oscillation just from the energy of the audio signal sending it into excitation (another radio term). 

That RFI (since that is what it is) can be as much as 30dB higher than the signal level itself! That can really mess with some preamps, especially solid state where the RFI can be rectified by the input stage, causing distortion, usually perceived as brightness. You can also get ticks and pops if the front end of the phono section overloads.

Hence the ’cartridge loading resistor’ which detunes the resonant peak, and by so doing reduces distortion.

Its much easier to built tube preamps that don’t have this problem! If the designer was aware of this problem it can simply be plug and play with no concern of the load resistor and far less ticks and pops (just the ones that are actually on the LP surface instead of ones generated by the phono section as well).

Since a lot of people find ticks and pops pretty annoying and since taking away a setup problem makes the whole thing easier, win win.  

@atmasphere Nicely explained. Is that the only reason (RF) that increasing the load resistor value appears to brighten (open) up the top end of a MC?

Another reason not to use transistor phono stage, and LOMCs. Just use MM/MI like in old good times.

Is that the only reason (RF) that increasing the load resistor value appears to brighten (open) up the top end of a MC?

@noromance If the load resistance is too high, the resonant peak can still make energy. RFI really messes with audio electronics; the more gain the more it seems to affect it. We're talking about this RFI injected directly into the input of the phono section via the tonearm cable itself. 

If you were able to install an RF filter than went low enough you'd find the problem eliminated in that manner as well but its easier to design the phono section to be immune to that in the first place. 

 Not really, a good ss phono stage is designed not to overload in the way  @atmasphere has outlined, a cheap one Wii have issues.  A cheap tube stage will also sound bad.  However, cheap and inexpensive are not the same thing.  For under $1500 the Hagerman Trumpet MC or MM is a great product.