Why don't we place the engine in the front of the wings?
They can be, as on the An-72/74, which has the engines mounted above and forward of the wings in part to increase lift, utilizing the Coanda effect.
One downside is that this makes access for maintenance more difficult, which is a large factor in operation costs.
https://en.wikipedia.org/wiki/Antonov_An-72
https://en.wikipedia.org/wiki/Coand%C4%83_effect