Ours is on a Sunday, albeit the one right before Christmas so kids off school/ many people finished for Christmas anyway (although of course we could be accused of being equally inconsiderate holding it so close to Christmas- luckily none of the guests we consulted before booking seemed to feel this way and all just said it would be a great way to kick off Christmas celebrations).
Sunday works for our immediate family and close friends, many of whom either don’t work Mondays, are teachers with that particular Monday off, or have enough flex that they can arrange to take the Monday off fairly easily. I know this because I checked with people first. Saturday doesn’t work for my sister, brother or best friend or in fact for me - though I know it’s terribly selfish of a bride to care whether the wedding date is convenient for her 
There will no doubt be some other guests who will have to be in work in the Monday or use a day’s annual leave. That is their choice - they can come, not overdo the drink and leave early, they can come and get shitfaced (partly if not entirely at our expense) and go to work hungover, or they can use a day’s annual leave. Or they can not come because it is not convenient for them. They are all valid options and I promise I will not be upset or arsey with anyone for choosing any of them. I won’t be made to feel selfish for making plans that work for us - the couple actually getting married and paying for the whole thing -our budget and the day we both hope for though. Plus to have had a Saturday wedding would have been at least £1500 extra, possibly more, so to afford that we’d have had to invite around 20 less people - so it was invite them on a Sunday or don’t invite them at all.
Seriously, I have travelled the length and breadth of the country and even internationally, taken time off work, arranged transport and accommodation for birthdays, the birth of children, christenings etc, or even just to see and spend time with people who matter to me - and when it hasn’t been possible to do that I’ve sent my love and everyone has got on with their lives. Why is it with weddings that couples are almost seen as selfish for holding the bloody thing in the first place? It’s bizarre. Go or don’t go, it’s one day?