Maybe there hasn’t been enough interest yet… But you can either make a feauture request or if there is one already, vote for that :)
You can request FLYPGS livery by creating a topic in #features and wait for people vote :D
I just looked for one and there is a request for the B738 livery :D
And if you also want to see their A320 fleet, you can vote for the topic here!
Please utilize the #features category and vote on topics linked above