I'm not sure what brothels you have been going to but over the years I have seen girls chilling on macbooks, on their phones, having chats, looking bored, agitated, anxious for a customer or going about their day. Maybe those Romanian brothels that traffic the poor ladies in on false promises look like that but not the latina ones I've gone to anyway 
. Not saying they are not out there.
Pimps and traffickers don't have to repeatedly beat, intimidate or otherwise interfere with the girls for them to understand and comply (grudgingly) the situation.
Bruising the women would be noticed by clients and more likely to bring about an intervention.
The thugs will be the lowest, taking most and denying the girls more liberties and unsurprisingly the experience for clients will be poor and highly suspect.
The "smarter" exploiters will have perhaps better looking girls, allow them their little happinesses and try to ensure the girls are kept busy printing money.
