Route Selection with equal AD’s

I had a interesting question from a friend today.

Assume the following scenario:

Im going to exclude any MPLS connectivity, as it is not relevant.
The PE (Router1) connects the CE (Router3) with two links, one serial and one wireless.
This particular ISP runs mostly static routes to client sites (within the VRF’s) or alternatively eBGP.

On a wireless link it is always good practise to run BGP to detect when connectivity with the remote end is lost in the underlying Layer2 network. (Preventing a blackhole)
Regarding routing on the Serial Link, there as a default route out from Router 3 and a static route to on Router1 pointing to Router3.

The client wants to load-balance traffic across both links. And the Admin Distance of the static route was set to 20 to match eBGP. (this is the scenario)

So the question : Why does Router1 not install both routes (the eBGP route and the Static), both with an prefix-length of /24,  a Admin Distance of 20, and metric of 0 into the RIB??

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