1. The argument here is that this may be the only money that a manager will receive during the first album cycle, and why should a manager work for an entire record cycle without receiving any compensation? Regardless of your feelings about this question, most established managers will not choose to do this. Therefore if you secure a deal without involving a manager, you should plan to set aside 15-20% of the advance in case you need it when you find a manager you like.
2. In choosing a record company and negotiating a record deal, many attorneys have divergent interests from the clients they represent. Often, the attorney is receiving a percentage of the advance from the deal and therefore may be incentivized to seek a front-loaded deal (i.e. one with a large monetary advance). Conversely, a manager has similar interests with the band, and may look favorably on a smaller advance from a company that they and the act feel better about. They might also choose to trade off the size of the advance to get better royalty rates or any number of other things. The largest monetary advance is not always the best deal.
3. For acts doing their first record deals, many lawyers will be too busy to get into lengthy explanations of the nuts and bolts of a deal. A good manager will take the time to teach their clients about the intricacies of the deal and the structure of each company so that the act can make informed decisions.
4. While some lawyers might help to shop acts to record and publishing companies, they do not have the interest or the time to spend countless hours working with an act on songs, performance, appearance, presentation, stage banter, etc. A good manager will take the time to help get you to a point where you are ready to be shopped for a record or publishing deal.
5. The final advantage to having a manager in the mix is that you benefit from two informed opinions of the lawyer and manager with differing perspectives while you start the very difficult and complicated process of negotiating your record and publishing deal-- or whatever deal may come your way.

All that being said, many bands opt to use their lawyer as de facto management for a variety of reasons. In some cases, they can’t find a manager, and in others, they don’t want one. Whatever the case may be, a lawyer can fill in some of the gaps, provided that they truly believe in your potential, and they have the time and inclination. As you can see, the role of an entertainment attorney can vary quite a bit depending on circumstances. However, regardless of your situation, an entertainment attorney is a crucial and necessary member of any artist’s extended team-- so before you do anything else, try to find one you trust.