I will answer as the amateur I am, and hopefully provide simple answers to the complicated subject you choose to tackle.
First of all, monkeys did not evolve into humans. Not even a portion of the monkeys in some isolated area of Africa. Monkeys and humans have a common ancestor. It's a huge difference. Each branch of the evolutionary chain adapted to survive in its own way. Similarly, humans are on one branch and various monkey species are several different branches.
Asking "why are there still....." questions suggests that it is all linear. Perhaps the presentations of evolution cause many to believe that. There is no single family of a species in existence with one set of parents. Maybe an easy way to understand this is to say that "If Asians followed the bison across the dry land of the Bering Straits, why are there still Asians in Asia?" We can all clearly understand that they didn't all go that way. (...and forgive me if that theory is not the accepted one anymore.)
Such questions as "Why are there still monkeys?" or "Why don't we see new species arriving today?" are creationist zinger questions. Ones they ask to stump people. There are answers, but since the answers cannot be framed in a single statement as the question was, they quickly shout "Checkmate, atheists!" and don't do the work of understanding the answer.
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As far as seeing macro evolution today, it's not like you could watch an old black and white movie from the 1920's and then another from the 21st century and note that the humans are different. It takes a wee bit more than your lifetime for changes to occur.
And further, as far as man is concerned, modern interactions interfere with "speciation," the evolutionary process by which populations evolve to become distinct species. If the Aborigines or the Japanese or any group on the planet remained isolated for several generations (granted, an amatuer like me doesn't know how many generations) then it would be likely that they could no longer produce offspring with outsiders because they finally became genetically different.
To take that to the animals, it does happen. But we don't see it easily because of the "several generations" things. Most hybrids of animals produce sterile offspring and don't allow for the creation of entirely different branches of the tree- think of the horse and donkey producing a mule; mules are sterile. But sometimes, speciation occurs and we have seen the results. Read up on the Galopogos Finch and see that it has occured. Even though many will say they are all still finches, apparently there are some different ones that cannot interbreed. So each will adapt separately and follow its own evolution.
And keep in mind that just as humans interfere with their own evolution by not staying isolated, humans also interfere with the evolution of animals. We give less and less space to wildlife and keep the land for ourselves. There is less and less chance that portions of a species will be isolated.
But if you are interested in seeing speciation in life that is a bit less complicated than animals, there are flowers and other plants that have been documented to evolve a bit quicker into separate species.
Experts, feel free to tear apart my layman's understanding. Otherwise, I hope it helps.