In the majority of settled areas personal given names are treated with less attention and importance than might be expected in real-world Western culture. When you know that you can simply refer to Chansey or Beldum and the other person will know who you’re talking about from context, differentiating between members of a species becomes significantly less necessary. This is especially true when there are only a small handful of pokémon of a given species living in a town or when the pokémon in question is especially famous or has an associated title, such as Guildmaster Delphox or any of the Custodian Guild’s Branch Leaders. Most pokémon who don’t personally know one of these celebrities don’t find their given names important enough to wonder about.
The purpose of a personal name is primarily to differentiate from the crowd, although many take great pride in their names and hope to see them become synonymous with their species. Inviting another pokémon to use your given name when it’s not necessary is generally considered a sign of casual familiarity, but as the number of pokémon of a given species frequenting a given area or social circle increases the accuracy of this rule of thumb equally diminishes. By convention, personal names come after a title and before the species name.
Think of it as being similar to defaulting to using last names and considering the “first name basis” a mark of honor or a result of needing more specificity.