Without going to specifics, a large reason for that may be that among those who say this are a large number who loudly push for unrealistic ideas masquerading t

Without going to specifics, a large reason for that may be that among those who say this are a large number who loudly push for unrealistic ideas masquerading them as constructive. Some may be honestly ignorant about it, but it is also unfortunately quite an effective way to derail any discussion and delay progress. See for example any suggestion about real world hyperloops.