Because if they don't people will continue to complain about the track lol.
I think the seats are a bad idea at this time. It's easy to see an empty seat but you can spread out on a bench and make the stadium look "more full". I'm not saying seats aren't more comfortable or anything like that, just that with the current situation retaining the benches might have been the best idea.
Also, I think this is a time where lots of schools, heck lots of different sports and pro teams even, are struggling to fill their stadiums. Times have changed, better access to the sports on television and such make it harder to get people out of the house. If I were in charge I'd worry less with adding seats and simply focus on making it the best looking, etc., we can make the stadium.
I'd lower it to complete the bowl, make the spacing extremely comfortable so that few seats are actually added, and I definitely wouldn't close in the bowl. WW is a great place and it can be made great again without sacrificing what it is now. Unfortunately it seems admin has part of that, fans are wanting another half, and we're ending up with a mix. It's not a terrible mix, but could be better.
I'd rather wait than do it wrong. The track has never bothered me and I've heard many visitors comment on how much nicer the stadium is (age not withstanding) than their own. But I think admin is being pressured to act now and it is legitimate pressure. Should have been done long ago, just wish they would get it right on the first try