I dance both Pro Am and amateur and really enjoy my Pro Am dancing and partner.
Here are some advantages:
1. Much less psychological friction on what is right or wrong. No fighting or lots of time trying to figure out who is right or wrong like with most amateur partnerships. You may even dance better without the mental friction.
2. Your Pro partner is going to be on time for lessons and is very available for practice or technical lessons.
3. A Pro partner is a partnership and they are more experienced and work better as a team. Some amateurs can be self centered and selfish. A good pro partner will dance at your level and abilities and will not try to out dance you.
4. Pro partners are available for hire,
it saves time compared to a extensive search for an amateur partner.
5. If you have a highly skilled Pro partner and you dance amateur too--you can use the pro as a dual role as a coach. This is very helpful, especially if you use the same competition loops or choreography.
6. If you loose your amateur partner you will still have your pro partner
to keep working on your dancing and keep your level up or even improve until another amateur comes along.
7. If you are a guy it's a good resource for you to find another amateur partner at Pro Am events. You can socialize and be on the look out for another amateur partner--and amateur ladies will see you dance and may even approach you about a partership.
Overall, there are several levels of Pro Am dancing from the higher serious level to the lower sort of social level.
Some ladies dance Pro Am just for fun and comraderie. The ladies will share the same Pro and go on competitions together and have fun. Some amateurs could be like Barbara Moore the standard Pro Am champ and spend loads of money on lessons and get someone like Igor to be their partner--this is a very high level of Pro Am dancing. There seems to quite a few "Doctor's wives" or indepently wealthy ladies that dance Pro Am at the higher level--the money for lessons has to come from somewhere.