At least we wouldn't have to put up with the idiots who drag themselves into the office despite being full of flu and end up infecting multiple people who will then end up having to take time off themselves. In that case one person who could have stayed at home for a few days has ended up causing several people to have to stay at home for a few days. I've had to deal with that on teams in work before where instead of just one person taking sick leave you've had several having to because that one person didn't.
Of course, I don't expect (nor want) a rule that means you have to stay home if you are ill. But I do hope that this will make people more aware that if they are ill, then maybe spreading that illness around isn't a great idea if it can be avoided. For some jobs maybe work from home for a day or two if you are sneezing all over the place several times a minute, and for others where being ill is actually grounds to not be in work (e.g. kitchen staff) I hope those rules are actually more tightly followed by managers who before this would bully staff to come in despite being ill.
I've said it before and I'll say it again. It's not always that simple.
A lot of companies will limit the amount of time you take on sick-pay. If you are off longer than that, you only get statutory pay. In fact I suspect in a lot of companies the only pay is statutory when off sick. In addition a lot of companies will required a "Doctors Note" if you are off for more than a certain number of days and that is hard to get (have you tried to see a Dr lately?). Not everyone can afford to lose the pay.
You can also be called in over the amount of sick leave or call you in to a meeting to explain yourself if you have taken "a lot" of sick time.
So I personally don't think people that are doing this are often doing it by choice. I suspect most people, if they are feeling ill, particularly with something like Flu would much rather stay at home in bed on full pay. The problem is they either don't have that choice or they will, at the very least, have to explain themselves when they are back in the office.
It's a difficult balancing act. If you give people unlimited sick days at full pay some will take liberties (I've worked at places where some staff are quite open about it and regard sick days as an extension of leave, so towards they end of the leave year, they go out for a good night and are hung over, just call in sick the next day). If too little, you end up in the situation you describe.