Most of the existing telescopes are located on Earth since it is easier and cheaper to construct, build and operate on Earth. Space launches are very expensive, and, moreover, if there is some problem with the telescope, orbiting in space, it is quite complicated to fix, since a team of astronauts has to be sent and work in open space is much more complicated than on Earth.
However, telescopes that operate in space offer a lot of benefits, comparatively to those on Earth, since the precision of the Earth's telescopes is limited by the atmosphere.
Hubble was a real breakthrough at the time of launch and discovered a lot of things and extended our knowledge about the space and Universe. As far as I understand, this progress would be impossible with any of the existing telescopes, located on Earth.
The upcoming launch of the Webb telescope is supposed to reveal a lot of facts about the early universe. In comparison to Hubble, this telescope has larger reflector: $~7$ meters for Webb vs $2.4$ meters for Hubble. In addition, it will be orbiting on a distant orbit far from Earth, with a radius of 1.5M kilometers. Therefore, there would be even less noise and hindrances in the observations.
Why do we actually need these, if they are located on Earth and will be limited in precision, comparing to the Hubble and Webb telescope? Is it the case, that they are solving somehow different tasks, and the huge diameter of the reflector will allow them to observe something that cannot be seen by either Hubble or Webb?