The reason is simple, the other passives on that row are better for our meta teams and actually it's not Neuro, it's mainly the other two, i barely see Neuro used these days.
Multiple healer teams are better with healing tips for obvious reasons.
Mabui/1010/Mei or Mei/Chojuro/Ao or any team that use water ninjas as primary damage dealer are better with water damage boost.
Reserve seal itself is not bad as a passive, it just has no synergy at all with most common water teams because water main is used as support, for reserve seal builds water main has to be move 1 with other ninjas supporting it instead.