A five year expat contract suits some people, eg late 50s retired from another airline and wants/needs to do a few more years before hanging up his wings and spending his days on the golf course. Or prehaps someone with a fixed term leave of absence and a job to go back to.
It is not suited to someone younger who wants to stay permanently without the risk of being laid of in downturns. For being expendable the expats got housing allowance, school fees and tickets home. Some may have enjoyed tax advantages by claiming non residence in Singapore.
For those with contracts not being renewed, work out how much more you got compared to local terms during your time with SIA. Prehaps it was worth it to you, prehaps not.
EK and others in the sand pit are still employing. EK do a nice package with housing, school fees etc and its open ended. Trade off being having to live in Dubai. CX aren't too bad if you can take HKG.
BA, QF etc offer local terms only. Singapore is a developed country and a pleasant, (though expensive) place to live. SIA obviously feel that because of this they don't have to pay quite such a premium to attract pilots.