I don'T know why they did'nt keep one for expose in a train museum..
Unfortunately, the interest just wasn't there. At the time the Turbo's service life was coming to an end, all of the preservationists and museums were clambering over each other to preserve steam locomotives and decades old passenger cars. Essentially, it was whatever the people working in those museums and groups remembered from their younger days, and modern equipment was overlooked. As a result, the Turbos were scrapped, and it was only years later that their significance was realized. It is a really sad state to see that the fastest train to ever run in North America no longer exists...and the trains that replaced it can't hold a candle to it.
Unfortunately, not much has changed. Most museum and preservation groups are now focused still on steam, but also on first generation diesels, F-units, Alcos, etc...Modern equipment is once again overlooked. We should consider ourselves in Canada lucky that Exporail in Montreal has preserved one of the LRC locomotives (6921), and the TRHA's recent project is on the way to saving another (6917) from scrapping (and that one's no surprise...Jason Shron, who's heading up the whole thing, is a great lover of the Turbo and one of those who is grieved that none of them were saved...now he's determined not to let the same thing happen to the LRC!). Who knows what we'll look back on in the future and say "darn, if only we'd kept one of those". There have been a lot of truly unique and ingenuitive locomotives come and go in recent years, with none of them left behind...think of a lot of the MLW power, or CN's first comfort cab and "draper-taper" locomotives. These are significant to railroading, and there's a good chance they will leave without a trace. At the time of scrapping, they're just old, ugly locomotives, and surely there's another steamer somewhere that could be saved instead.
I do recognize that preservation groups and museums only have so much money to work with. At the same time, there is no doubt that preservation efforts often become biased towards certain time periods, and result in the loss of what will become valuable in the future. The Turbo is a perfect example.