Refusing to Offset the Vote in Knesset

The Knesset is set to vote today on the "minimarket law" that would give the Minister of Interior the right to reject a municipal law, including a law passed to allow businesses to open no Shabbos.
The coalition is running into a problem. MK Yehuda Glick's wife passed away this morning and Glick, obviously, will not be able to participate in the vote. The coalition has been having trouble garnering enough support for this bill and if it passes it will be by the skin of its teeth. Losing an MK that would vote for this bill, hurts the chances of it passing. And, this is in addition to MK David Azulai from Shas who is still hospitalized.
Normally there is an unofficial arrangement in the Knesset by which when MKs from either side are unable to attend a vote, an MK from the other side will offset that and not participate as well. In this vote today, the coalition MKs are refusing to agree to offset the ranks for Glick (and Azulai).
I would note that a couple of weeks ago when the minimarket law came up for ts initial reading, opposition MKs also refused to offset the vote for Azulai who had just been hospitalized. At the last moment Meretz chairman Ilan Gilon showed compassion and said that being moral and human is more important than taking advantage of the moment and agreed to offset Azulai's vote.
Notwithstanding my following question, being that such an arrangement does exist and is almost always followed, it is immoral for them to refuse to offset the vote and take advantage like this of the passing of Yaffa Glick. This is not even as important a vote as they are making it out to be because we all know it will pass and legal counsel in the government has said it will be applied retroactively as well.
In normal situations, not including today's vote, I would mention that I never really understood the concept of offsetting the vote for missing MKs. Why is it the moral obligation of the opposition MKs to help a coalition law, that they oppose, to pass? If the coalition doesn't have the necessary votes, for whatever reason, they can delay the vote until they get the numbers. Why does it fall on the opposition's shoulders? They normally both gain from the arrangement as neither side needs to be overly pressured to make sure they have full attendance - but to turn that into some moral obligation that has to be followed? I don't get that..
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