What do you mean by "forced"?
Physical fear of death or injury? Having a gun put to your head?
Some women experience something very like this - organised crime gangs are involved in the surrogacy in many parts of the world, and women and girls are literally trafficked into this foul industry and kept perpetually pregnant, in the same way that many are forced into and trapped in prostitution. There are also documented cases of children paedophiles using surrogacy obtain children.
Forced by poverty? - a huge reason for many, if not most women. Why would any woman risk her life for money knowing that she could die and leave the children she is doing it for without mother?
Forced by societal pressure? Massive cause in many so-called "altruistic" surrogacies. Families putting on pressure a woman to have a baby for sister/ auntie/ cousin whatever. You can't even imagine how great this pressure is for many women in all cultures.
And there are accounts of husbands who realise that their wives fertility provides an easy way for them to get money, and push their wives into surrogacy even though they don't want to.
In addition, very few agencies properly explain the risks involved in being pumped full of hormones, or carrying a baby, or giving birth even in this day and age in the first world. And many, many women don't have first world advantages for medical care.
And many commissioning parents look for ways to avoid paying the full fee, and course don't tend to favour the surrogate.
There are absolute horror stories out there - and many aren't just from the perspective of the surrogate, but looking at what has happened to the infants is chilling.
https://www.theindiaforum.in/article/surrogacy-biomarkets-india-troubling-stories-2021-act