Removing the numbers for trademark holders is an imperfect solution though, though, since multiple entities can hold the same mark so long as they are in different markets.
A critical test for trademark violation is "does it cause confusion in the marketplace?" and if nobody confuses Oracle Software with HiSpec Oracle trailer tires or Oracle Lighting, they're all allowed to hold a trademark on "Oracle". But if you're talking about a namespace where "there can be only one", which of the entities who holds a registered trademark wins?
There are assuredly better solutions, but even an imperfect solution is better than the current state of things. First-come-first-serve with unique per-site screen names just plain sucks.
edit: I agree the randomness is important. Without random numbers, the first person to get in will pick "0069".
Platforms should also consider accommodations for trademark holders. Most have some sort of program, but it seems to be a mess. If every normal screen name has a numeric code at the end, there's room to give trademark holders a non-numeric name without having to seize a handle from someone else. The spot normally occupied by the numeric code could be replaced with an indication that that account is owned by the trademark holder or with the name of the entity that owns the trademark, to differentiate it from normal accounts and also from any accounts that might hold a similar mark in a different business.