Don’t let her watch tv. I have a bored jar so if the kids need something to do then they pick from the jar. Half of the items are chores and half are fun activities that are not screen time related. Eventually they get enough chores that they stop hounding me for things to do. To answer your question, it’s because we give them free rights to the tv.

SO used to be Disney Daddy who made his entire world and all his time 110% her every second she was around but that has changes massively in the last 2 years. We just straight up give her all her options, tell her that we are not her entertainment, and go back to our bussiness. Do it enough times and they get the message. Limit TV as much as you can, though some days I understand letting them be because you get sick of it. 

The SDs learned to not say the bored phrase with me around. Oh, well, if you need something to do you can clean your bathroom, mop the kitchen floor, weed the front yard, etc, etc. There was none of that when I grew up and none now.

my three children (now in their 20's) never got bored! we never had a computer and fancy TV with a million channels! the three step children have to be constantly entertained or they immediatley become bored! once they are bored they misbehave... I am trying very hard, to teach them and my partner ways to have fun without screen time, but it is hard when it has been used as a babysitting tool for so long! The worse time is the car, they will fight in the car unless they are doing something, it was most apprent when myself my own biologic daughter (then 18) and his three children went on holiday the other year...the long journey was hard as they want to fight when in close promintry of each other, to the point where my partner doesnt want to take long car journeys even 20 mins is too much if we are all in the car together! My daughter was baffled by it! she taught them loads of car games to entertain them which we still use now. It's amazing and scarey how ovr 10 years kids have become so relient on being entertained rather than finding their own entertainment, or just sitting quietly and looking at the world go by! I feel so lucky my children didn't have the whole social media problems when they were 10!

This is where society has gone. When I was little, we went outside and played for hours with friends. We weren't even allowed back inside, lol, we drank water from the hose and every now and then, someone's mom would give us popsicles.  It never occurred to me to ask my mother to play with me.  My father would throw a ball with me, or play a board game when he got home from work, but that was a treat, not the norm.

Kids are the center of every family now. Everything is about them. They have 8 bazillion toys bought for them, and 14 different activities that parents schlep them around to.  Why would they not think they are entitled to non-stop entertainment from the adults? Also - nothing can compete with electronics for some kids. 

I have officially entered the "Get off my lawn" age.
 

People are much more cautious about letting their kids run around the neighborhood and play.  I don't know if it is more dangerous now, but it does not matter, if there are not kids running around (and in most neighbohoods, they don't), you cannot send kids out to play.  Families were bigger then, and no one is sending a kid out by himself.   Stepkids are less likely to have friends in the nieghborhood if they are not there all the time.  

Many kids do organized activity and are not availaible.   This is not a movement by divorced moms, many kids where I live are in intact families and they participate.

I agree, hard to compete with electronics. OP notes the kid has taken over the TV.  I have to ask, does that mean there is one TV and OP wants to watch adult shows?  Maybe try to agree on a show all can watch, a nature show, etc?