Simple answer : lambda probes do not work with high leaded fuel, the lead deposit on the probe leds to a ´drift´ in indicated O2 content.
And of course all ´modern´ aircraft injection systems are 100% mechanical, so no interference with electromagnetic fields, higher reliability (?), lightning strike safe etc.
On the other hand, a good hand mixed engine is better than an electronically controlled one. The signal of the lambda probe is rapidly changing at lambda=1 and more or less just ´high level´ or ´low level´ for lambda >1 or > 1, so it is perfect to adjust air to fuel ratio at exactly lambda=1. (which you need for the catalytic converter in motorcars) It is poor in adjusting any other lambda.
In Aircraft engines, we use lambda < 1 for takeoff power (best performance, economy is not relevant for this short period, internal cooling due to fuel, so higher peak performance allowed, HC and CO emissions are irrelevant) and lambda > 1 for cruise (best economy, the bad throttle response is irrelevant as we don´t change the throttle setting in cruise, NOx emissions are irrelevant). If we would fly with lambda = 1 all the time, takeoff power would be lower and cruise would be less economical.
(Both effects might be compensated by the better quality of the fuel injectors and hence better fuel vaporisation if you change to electronically controled injectors and high pressure fuel supply)