For the record, Marriage doesn't necessarily mean having sex. Many marriages are sexless later in life.
On the legal obligations you have to look at them one by one. You can't lump them all together. Tax benefits were put in place to encourage marriage under the assumption that it leads to a more stable society. If any coupling is seen as to lead to the same outcome then tax laws should change to accommodate them. Getting people to agree to that is something else.
For decision making ability, power of attorney agreements can serve similar purposes. Properly written wills can simulate other marriage benefits. Partnership agreement can cover financial issues. For childless relations marriage isn't really needed and should probably be avoided.
On the legal obligations you have to look at them one by one. You can't lump them all together. Tax benefits were put in place to encourage marriage under the assumption that it leads to a more stable society. If any coupling is seen as to lead to the same outcome then tax laws should change to accommodate them. Getting people to agree to that is something else.
For decision making ability, power of attorney agreements can serve similar purposes. Properly written wills can simulate other marriage benefits. Partnership agreement can cover financial issues. For childless relations marriage isn't really needed and should probably be avoided.
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