Why does this ggridges plot implies negative values when there are none?

Question

library(ggplot2)
library(tidyverse)
library(ggridges)

data(iris)

ggplot(iris, aes(Petal.Width, Species))+ 
  ggridges::geom_density_ridges()+
  coord_cartesian(xlim=c(0, 4))+
  theme(panel.grid.major = element_blank(), panel.grid.minor = element_blank(),
        panel.background = element_blank(), axis.line = element_line(colour = "black"))

This ggridges visualization implies that some petal widths for setosa and the others are below zero, but this shouldn't be possible since there are no negative values in the dataset. I am wondering why the visualization shows negative values being in the data at some frequency?