Ok what I'm about to say can't really be supported with any evidence but I wanted to just throw the idea since I was always finding strange how among all the senju, Hashirama was the only one who could use wood style.
I think that his use of wood style might be a technique that was handed to him by the uzumaki clan, maybe as an offer to have peace with them in exchange for a marriage with one of their priestess and more specifically with Mito Uzumaki. You might say how I came to this conclusion, well the simple reason is because I couldn't find anything else that made Hashirama special in terms of his other clansmen other than the fact that he was married with an uzumaki priestess, a powerful one, considering the fact she could keep under contol the whole Kurama.
And now here it comes another theory which I used to come to such a conclusion. Basically, I believe that the sage was an uzumaki
My point is that if the sage was indeed an uzumaki, maybe the wood style passed down in fact on uzumaki while the senju had only that powerful body. The reason for not seeing any of the uzumaki using it is because they might deem it as a forbidden jutsu because of its overwhelming strength ( I mean just look at Hashirama's wood style abilities, he even has access on the 5 basic elements!) and they decided to give it only to Hashirama only because they were certain of their good will. P.S The reason for being wiped out was supposedly the fear other villages had for the uzumaki as they regarded them as powerful, the possesion of wood style could be an extra reason for being regarded as such.
Thing is that we don't know when Hashirama got married or when did he first use wood style for the first time, he was only seen using it at such age where he could have been married.
My aim is not persuade you since I clearly can't with the arguments I have ( especially if you're against the uzumaki theory) but rather to introduce an idea which I found interesting. I mean, I for one, would prefer that to be the case than Hashirama having for some inexplicable reason the unique ability to use such a kekkei genkai which normally requires only the simultaneous use of earth and water style ( don't say that that it's not difficult but surely other people would have the capacity to do that as well, Hiruzen for example).
I hope you found my theory interesting =D
I think that his use of wood style might be a technique that was handed to him by the uzumaki clan, maybe as an offer to have peace with them in exchange for a marriage with one of their priestess and more specifically with Mito Uzumaki. You might say how I came to this conclusion, well the simple reason is because I couldn't find anything else that made Hashirama special in terms of his other clansmen other than the fact that he was married with an uzumaki priestess, a powerful one, considering the fact she could keep under contol the whole Kurama.
And now here it comes another theory which I used to come to such a conclusion. Basically, I believe that the sage was an uzumaki
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. My point is that if the sage was indeed an uzumaki, maybe the wood style passed down in fact on uzumaki while the senju had only that powerful body. The reason for not seeing any of the uzumaki using it is because they might deem it as a forbidden jutsu because of its overwhelming strength ( I mean just look at Hashirama's wood style abilities, he even has access on the 5 basic elements!) and they decided to give it only to Hashirama only because they were certain of their good will. P.S The reason for being wiped out was supposedly the fear other villages had for the uzumaki as they regarded them as powerful, the possesion of wood style could be an extra reason for being regarded as such.
Thing is that we don't know when Hashirama got married or when did he first use wood style for the first time, he was only seen using it at such age where he could have been married.
My aim is not persuade you since I clearly can't with the arguments I have ( especially if you're against the uzumaki theory) but rather to introduce an idea which I found interesting. I mean, I for one, would prefer that to be the case than Hashirama having for some inexplicable reason the unique ability to use such a kekkei genkai which normally requires only the simultaneous use of earth and water style ( don't say that that it's not difficult but surely other people would have the capacity to do that as well, Hiruzen for example).
I hope you found my theory interesting =D