The business fashion has envolved over the years, today lots of professional women choose more relaxed looking clothes, not necessary formally matching two-piece suits or dress coats. Letizia's clothes are fine for a career woman going to work, I think that's the look she is after, she just wants to look normal, not luxurious.
I think her hair and makeup usually look pretty good for someone without the professional help. It's fine for a daily royal act. However for some big day time events, ex. national day, state visits or oversea trips, she should get hair professionally done, especially for the oversea trips with a different weather, if the SRF doesn't like hiring a local hairdresser, then bring one to the trip (Sofia always has a hairstylist).
How do you know she and Felipe don't work 8-10 hours a day ? I always heard they prepare acts down to very details, sometimes knew more than the people who organized the acts, on top they have 3 foundations (two very big ones, PoA and PoV).