I'm always relieved when someone does that. I'm too shy to do it myself, and have gotten quite burned several times. Now that I'm actually finacially stable, it does matter so much, but in the not-so-distant past it's led to some very uncomfortable situations. I think mostly people who are used to splitting really don't notice what other people are having.
DH and I don't drink, and we went out with a large group of his friends. We were also quite tight on money, and only ordered £7 entrees to eat. Everyone else had starters, desserts, alcohol, other drinks, etc. When it was done, the split came down and we were told it was £40. We were a bit shocked, being over twice what we had expected to pay, but we stumped up because we figured it was the cost of being social. Then it came out it was £40 per person! DH went ballistic, and they sorted it out with us just paying the one £40.
A few years before we went on a group holiday, and the first dinner out was split. DH and I used half our food budget that night, to pay for some small entrees at a fraction the cost. One friend noticed and spoke with us, and then I assume others, and we didn't do that for the rest of the holiday -- good thing, as we had to eat very sparingly for the rest of the week.
Just last night we had a work dinner out -- work was subsidising the out-of-town guest plus a little extra. Because I don't drink and had no dessert, I actually ended up paying about £3 more than my meal, whereas everyone else got a bit of a discount. Not a problem for me now, although a little annoying that I paid extra to socialise for work, but I just think the splitting thing has too much unknown in it.
I'm afraid that represents 75% of my bill splitting experiences, only having had one more where all 4 people ordered exactly the same thing and it made perfect sense.
Unless you're really confident that everyone in the group is finacially comfortable, I think paying what you order make the most sense as a default.