No Mode "C" in many light A/C
BIK_116.8
The problem is that that many light aircraft transponders are mode "A" only. In order to report altitude they would need to either upgrade the altimeter and/or the actual transponder at some considerable cost. Many owners would not do that unless it was a legal requirement.
As for conflicts at low level this is how I cope.......
In UK controlled airspace it is very unusual to get such a situation apart from the helicopters in and out of Battersea - thus I accept that TA's will sometimes occur with little actual risk. If the traffic is mode "C" equipped and notified as as conflict (India 99 etc) then I am allowed to switch my TCAS to TA only thus avoid an RA. It would do this automatically at very low level anyway.
In the USA it is becoming standard practice on parallel approaches to switch to TA only as seperation standards are very tight and in good weather most crews elect for a visual approach hence work under "see and avoid" principles.
If I receive an RA and cannot instantly visually aquire the traffic I will react as per SOP's even if that requires a go-around......