Why more women's clothing sizes so always look old lady?

No offense intended. I am not a grandmother and I do not want to look like to one. Where can I find the smaller size (which is 16 and up) that are stylish, but not necessarily fashionable, that do not cost a fortune? I have three kids to dress too, so I'm on a budget and can not afford $ 40 shirts and pants $ 80 U.S. dollars.

Old Navy has a more – but I think it might be online only. but they tend to have good business

JMS/Just My Size Launches New Womens Plus-Size Clothing …

Floral Romper – Womens Sizes $14.99 This easy to wear romper is styled for comfort with an all-around elastic waist and side seam pocket. Polyester. Imported. Machine wash and dry. Approx. inseam 2″. -Availale in Sizes:1X(16W-18W), 2X(20W-22W), 3X(24W-26W) or 4X(28W- 30W) ;

Cobbler Apron – Womens Sizes $11.99 Lovely cobbler apron has a snap front for easy on/off and two handy front pockets. Woven cotton/polyester. Easy-care machine wash and dry. Imported. Specify size and color on order. Approx. lengths listed. -Availale in Sizes: 1X(16W-18W), 2X(20W-22W), 3X(24W-26W) or 4X(28W-30W) (29″) ;

Venetian Lace Nightgown – Womens Sizes $19.99 nit. Easy-care machine wash and dry. Imported. -Available in Sizes: 1X(16W-18W), 2X(20W-22W), 3X(24W-26W) or 4X(28W-30W) (53″) ;

Embroidered Floral Dress – Womens Sizes $21.99 This perfect summer dress is accented with lovely floral embroidery. Machine wash and dry. Imported. -Availale in Sizes: 1X(16W-18W), 2X(20W 22W), 3X(24W-26W) or 4X(28W-30W) (45″) ;