Priority Pass

Priority Pass is a product that potentially provides consumers with access to airport lounges that Priority Pass has contracted with.
The word "Priority" is somewhat of a misnomer.
What has been prioritized is alliteration over accuracy.
Priority Pass allows airport lounges to bring in incremental revenue by providing access to Priority Pass members if space is available during a given time.
Think of the relationship between Priority Pass and airport lounge operators as being the opposite of that between Burger King, McDonald's, Wendy's, and their franchisees.
Once constructed and in operation, a fast food franchise must strictly comply with the chain's rules.
In contrast, airport lounges are often constructed as a perk for an airline's highest valued passengers.
A collection of airport lounges or an individual airport lounge might choose to affiliate with Priority Pass but even then Priority Pass does not have the ability to dictate the terms of the relationship.
Out in suburbia, Burger King seems to be able to find space for a franchise across from, if not outright adjacent, to a great number of McDonald's franchisees.
Airport lounge space is a less elastic resource.
Other than discriminating against any legally protected classes, airport lounge operators have discretion over who to admit.

Acquiring A Priority Pass Membership

A Priority Pass membership can be acquired as either a benefit of a credit/charge card product or purchased directly on the Priority Pass website.
As result of Priority Pass memberships with increasing numbers of credit cards, the number of memberships has greatly expanded.
Initially airport lounge operators responded to the accompanying expanded demand by creating additional blackout times for members who acquired the membership bundled with a credit product.
During that time, those additional blackout times could have been an edge case where purchasing a membership outright might have made sense versus receiving a membership as a benefit of having a credit product.

Now, however, expanding blackout periods exist but to the best of my knowledge those blackouts are without regard to how one acquired his or her membership.
Given that there is now little, if any distinction, between whether one's Priority Pass membership were purchased directly or bundled with a credit product, there is little case for directly purchasing a membership directly.
Below are edge cases where you could plausibly justify purchasing a Priority Pass membership directly instead of getting one that is bundled with a credit card, but most people would be better off waiting for either or both of the conditions to be resolved.

1. You have a limited credit history or are in the process of rebuilding your credit.
   Some, but not all, of the credit cards that bundle Priority Pass membership are premium products that might require a minimum credit limit of $10,000 or more in order for the product to be approved.
2. You are about to apply for a mortgage and do not want to do anything that would impact your credit reports.

Airport Restaurants

The Priority Pass business model may not scale well, at least from the perspective of the consumer.
When there was a smaller number of Priority Pass memberships in circulation, at a given airport there may have been more not fewer airport lounges that accepted Priority Pass than there is now.
As the number of Priority Pass members grew, some airport lounges restricted hours of access for Priority Pass members or left the program altogether.
To counter this, Priority Pass allowed the membership to be used for credit at specific airport restaurants.
There are two issues to be aware of with this:

1. A given type of Priority Pass membership might allow for an unlimited number of uses per year, a small finite number of uses per year, or each use might mean being charged a fixed fee.
   If there is a fee per use, it is your responsibility to make sure the value you get from the lounge or restaurant is at least as great as the per visit fee.
2. Priority Pass memberships acquired as part of an American Express charge or credit account may be used at airport lounges but NOT airport restaurants.
   If a specific airport lounge accepts American Express cards you can pay with your American Express, but not with a Priority Pass associated with the American Express account.