Not to sound too defensive, Mamasaanan, because I've seen the same small teats on Nigerians, but honestly there has been a lot of improvement in how milkable these little goats are. I have certainly seen teats on standard dairy goats that were no larger than the teats on either of my Nigerian does.
One thing I HAVE found out, in my standard goats and in my Nigerians, is that it really does help to have 12 hours between milkings in early lactation to develop teat size and udder capacity, especially in a first freshener. For myself, I separate the kids at night after the second or third night, and let them stay with mom during the day, whether I'm milking the doe or not. If I'm not milking, the kids get a big breakfast, but the mom still gets the opportunity to develop properly, just like all those standard dairy goats that don't dam raise their kids.
I find the real differences between the small and large goats are 1) amount of milk - duh! - 2) quality of milk 3) ease of handling - another duh! - and 4) persistence of lactation. 1) I have some outstanding standard dairy goats that are currently drowning me in milk. I'm only milking two of the three, and they're raising their own kids, yet I'm throwing out nearly a gallon of milk a day. What a waste! 2) I've had milk from a lot of different standard goats and NOTHING comes close to Nigerian milk for downright tastiness, but then, I really like rich, sweet milk. I guess someone who prefers less sweetness and butterfat might form a different opinion. 3) It's just natural that a 60 pound goat is a whole lot easier to handle than a 150 pound goat. 4) Persistence of lactation is a biggie for me because I only like to milk once a day. My Obers can maintain a relatively level lactation on that schedule, but the Nigies tend to dry off fairly quickly.
I'm now breeding minis to try for the persistence of lactation from the standards, along with the ease of handling and delicious milk in more reasonable quantities from the Nigerians. We'll see how it goes.