250kt - you are correct. Direct tracking is available and utilised in Australia on a daily basis. Only when the airspace/traffic mix becomes too complex does anyone fly the SID to its full extent. Most SIDs are cancelled leaving 5000agl (a silly noise thingy) for jets or 3000agl for turbos. Where the SID goes thorugh someone elses airspace or ahs VNAV for separation then SID cancellation may be more difficult - but this is not because we cant do it - we can with Coord.
STARs are usually flown in thier entirety due to the linkin with the expected approach procedure, although even then track shortening within the procedure is given - somewhere that the FMS can rejoin without too much fuss.
Not sure where Mikk is from but I know and have written LIs that allow track shortening in given airspaces in given time frames. Cuts out the tiresome coord!!