How can we tell it is absolutely necessary?

0Hi,02br
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00I was looking at the Collins Cobuild Compact English Learner's Dictionary for the word 'experience' and it had this example sentences in addition to many others.02br
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01i00Widows seem to experience more distress than 01u00do02u00 widowers. 02i02br
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00My concern deals with the underlined part. I feel that it is correct to place it because the the act of 'experencing' requires some 'do' action parts and thus, putting 'do' seems to make the sentence correct or in some instances make the likes of it flow better.02br
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00But sometimes, I am inclined to do without them, am I wrong to do that? How can we make the right choice if I am confronted with the same dilemma in the future?02br
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01i00Widows seem to experience more distress than widowers. (Wrong? Why?) 02i02br
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00How about these?02br
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01i001. John seems to play basketball better than do Sam.02i02br
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01i002. John seems to play baketball better than Sam.02i02br
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01i003. John seems to play basketball more intensely than do Sam.02i02br
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01i004. John seems to play basketball more intensely than Sam. 02i0-