This is one of those things that has always bothered me along with the lack of weapon diversity (see everyone running with double axe/bladed staff).
The benefits of Bushido are too good to miss whether it be increased damage through Perfection, especially on non slayer vulnerable enemies or through increased damage for whirlwind and counter strike, extra healing and stamina regen through confidence, complete damage mitigation from evasion and of course combined with Parry a higher chance to parry than a pure parry warrior providing you use a 2 handed wepon. There is also the mana cost reduction for special moves for having 300 points across certain skills which almost certainly would include a weapon skill, Parry and Bushido. The other benefit of being 'forced' down the 2 handed weapon route is you will easily cap out all stats on your weapon due to the increased imbue cap where a one handed weapon will not.
For any play these days, Bushido is almost critical to play successfully (not for everything, don't jump on that bandwagon). And the result is you simply can not use a shield, and using a one handed weapon without a shield would be pointless.
I've heard the argument a million times "But you have to consider all the extra stats you get on a shield", absolute nonsense! See all the benefits I've listed in para 2 above, there is absolutely no way in hell you can make up all those lost stats/abilities on a shield, it's just insanity.
The other argument "But that's the benefits you get for spending an extra 100+ point in Bushido". That's fair enough, but I don't want to be forced down the 2 handed route and run around with a double axe/bladed staff like 99.999% of all other players. A one handed/shield user should not be crippled for spending an extra 100+ points in a skill.
I understand from a lore perspective that those who practice the art of Bushido would not use shields, but they sure as hell would not use double axes either!!!
Using a double axe should cripple Bushido users the same way it cripples shield users!