Ah, thanks for explaining. It seems I misunderstood ?alias and thought it to be a variant of ?userinfo - my bad.
Still, it is probable that not all zone admins on Isometry would have the same standards regarding the confidentiality of alias information. On SSC, for instance, zones like TW have a policy of strict confidentiality of players' alias information; any disclosure of alias information to the public is strictly prohibited. And with the old SSCC alias system, access was closely limited to help safeguard against abuse.
Yes, zone admins can put up their own alias bots, but that would restrict them to collecting information from players that actually enter their zones; if a player never enters "Zone B", their alias information would never be directly available to ops of "Zone B". Whereas with a biller-based ?alias command, even if a player has only ever played in "Zone A" on Isometry, his/her alias information would be freely available to ops of "Zone B", "Zone C", etc. on Isometry - and some of these ops might have a grudge against the player in question, and might disclose the players' aliases to the public.
I am not saying whether this is good or bad, but this is something that players do not have to worry about on SSC.