I play electro-acoustic guitar in my band, and go straight into the PA. This is fine when we have our own PA, but frequently we have to use the venue's PA and mixing desk. You can face various situations:
- XLR cable snake to a mixing desk 20m away;
- No DI boxes available;
- Mixing desk is low quality with only mic inputs;
- Mixing desk has no phantom power.
I have had all these, and a DI box like this is invaluable because it can be battery or phantom powered, it has pad switches to reduce the output, and it is robust and cheap! If I was using my own DI all the time I would proably get a more expensive "industry-standard" DI, but this is fine for occasional use.