This is late midgame (2275) for one of my trade routes. The Max Piracy here is 420.83 and will likely go up a lot more as trasde value rises. Now, in theory this isn't a problem. Except the protection in comparison seems incredibly small and insufficient. Even several patrolling fleets would not be able to suppress this. It would take roughly seven fully upgraded Hangar Starbases to deal with this.
Just as a reminder, we have a tradition that adds a grand total of 5 trade protection! One could change that tradition to 50 and it would still do virtually nothing.
While I can agree that trade defense measures is an issue (I'd support % decreases rather than flat bouffs), the discussion in the threat misses a point-
Trade Builds incentivize relatively tall/habitat builds, rather than wide-conquest. It is, to some degree, an anti-conquest meta.
While this can be circumvented (have trade jobs in empire interior, industry on exterior), and as a whole makes trade builds less meta, this is a good gameplay pressure
if trade-builds can be good enough to justify it. It creates an incentive to not conquer other empires (because you can't defend trade lanes), incentivizes late-game conflicts (when gateways allow trade management), and adds an instability risk-reward factor.
This does, in meta terms, make it 'not as good' in many respects- and I feel habitats come too late to really build your build around- but it should be noted trade-build piracy protection is a limiting mechanic against unrestrained conquest.